{"id":"CVE-2026-44660","aliases":["DEBIAN-CVE-2026-44660","EUVD-2026-32663","GHSA-c38f-wx89-p2xg","OESA-2026-3606","OESA-2026-3607","OESA-2026-3608","OESA-2026-3720","PYSEC-2026-2293","SUSE-SU-2026:23114-1","SUSE-SU-2026:23136-1","SUSE-SU-2026:3539-1","UBUNTU-CVE-2026-44660","openSUSE-SU-2026:21518-1"],"status":"published","title":"UltraJSON: Memory Leak in ujson.dump() on Write Failure","description":"UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.","severity":{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00421,"percentile":0.36728,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-401"],"published":"2026-05-12T22:25:11Z","modified":"2026-11-09T12:49:51Z","fixes":[{"ecosystem":"PyPI","package":"ujson","fixed_in":["5.12.1"],"sources":["ghsa","osv"]},{"ecosystem":"Debian:14","package":"ujson","fixed_in":["5.13.0-1"],"sources":["osv"]},{"ecosystem":"SUSE:Linux Enterprise Server 16.0","package":"python-ujson","fixed_in":["5.10.0-160000.3.1"],"sources":["osv"]},{"ecosystem":"SUSE:Linux Enterprise Server for SAP applications 16.0","package":"python-ujson","fixed_in":["5.10.0-160000.3.1"],"sources":["osv"]},{"ecosystem":"SUSE:Linux Enterprise Module for Development Tools 15 SP7","package":"python-ujson","fixed_in":["1.35-150100.3.13.1"],"sources":["osv"]},{"ecosystem":"SUSE:Linux Enterprise Module for Package Hub 15 SP7","package":"python-ujson","fixed_in":["1.35-150100.3.13.1"],"sources":["osv"]},{"ecosystem":"SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS","package":"python-ujson","fixed_in":["1.35-150100.3.13.1"],"sources":["osv"]},{"ecosystem":"SUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS","package":"python-ujson","fixed_in":["1.35-150100.3.13.1"],"sources":["osv"]},{"ecosystem":"SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS","package":"python-ujson","fixed_in":["1.35-150100.3.13.1"],"sources":["osv"]},{"ecosystem":"SUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS","package":"python-ujson","fixed_in":["1.35-150100.3.13.1"],"sources":["osv"]},{"ecosystem":"SUSE:Linux Enterprise Server 15 SP4-LTSS","package":"python-ujson","fixed_in":["1.35-150100.3.13.1"],"sources":["osv"]},{"ecosystem":"SUSE:Linux Enterprise Server 15 SP5-LTSS","package":"python-ujson","fixed_in":["1.35-150100.3.13.1"],"sources":["osv"]},{"ecosystem":"SUSE:Linux Enterprise Server 15 SP6-LTSS","package":"python-ujson","fixed_in":["1.35-150100.3.13.1"],"sources":["osv"]},{"ecosystem":"SUSE:Linux Enterprise Server for SAP Applications 15 SP4","package":"python-ujson","fixed_in":["1.35-150100.3.13.1"],"sources":["osv"]},{"ecosystem":"SUSE:Linux Enterprise Server for SAP Applications 15 SP5","package":"python-ujson","fixed_in":["1.35-150100.3.13.1"],"sources":["osv"]},{"ecosystem":"SUSE:Linux Enterprise Server for SAP Applications 15 SP6","package":"python-ujson","fixed_in":["1.35-150100.3.13.1"],"sources":["osv"]},{"ecosystem":"openSUSE:Leap 16.0","package":"python-ujson","fixed_in":["5.10.0-160000.3.1"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"5.12.0"},{"fixed":"5.12.1"}]}]},{"source":"osv","ecosystem":"Debian:12","package":"ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.10.0-1","5.11.0-1","5.11.0-2","5.11.0-3","5.13.0-1","5.7.0-1","5.8.0-1","5.9.0-1"]},{"source":"osv","ecosystem":"Debian:13","package":"ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.10.0-1","5.11.0-1","5.11.0-2","5.11.0-3","5.13.0-1"]},{"source":"osv","ecosystem":"Debian:14","package":"ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.13.0-1"}]}],"versions":["5.10.0-1","5.11.0-1","5.11.0-2","5.11.0-3"]},{"source":"osv","ecosystem":"PyPI","package":"ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.12.1"}]}],"versions":["1.15","1.18","1.19","1.21","1.22","1.23","1.30","1.33","1.34","1.35","1.4","1.6","1.8","1.9","2.0.0","2.0.1","2.0.2","2.0.3","3.0.0","3.1.0","3.2.0","4.0.0","4.0.1","4.0.2","4.1.0","4.2.0","4.3.0","5.0.0","5.1.0","5.10.0","5.11.0","5.12.0","5.2.0","5.3.0","5.4.0","5.5.0","5.6.0","5.7.0","5.8.0","5.9.0"]},{"source":"osv","ecosystem":"openEuler:20.03-LTS-SP4","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.0.2-3.oe2003sp4"}]}],"bundled":5},{"source":"osv","ecosystem":"openEuler:24.03-LTS-SP1","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.1.0-6.oe2403sp1"}]}],"bundled":4},{"source":"osv","ecosystem":"openEuler:24.03-LTS-SP3","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.1.0-7.oe2403sp3"}]}],"bundled":4},{"source":"osv","ecosystem":"openEuler:24.03-LTS-SP4","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.1.0-6.oe2403sp4"}]}],"bundled":4},{"source":"osv","ecosystem":"PyPI","package":"ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.12.1"}]}],"versions":["1.15","1.18","1.19","1.21","1.22","1.23","1.30","1.33","1.34","1.35","1.4","1.6","1.8","1.9","2.0.0","2.0.1","2.0.2","2.0.3","3.0.0","3.1.0","3.2.0","4.0.0","4.0.1","4.0.2","4.1.0","4.2.0","4.3.0","5.0.0","5.1.0","5.10.0","5.11.0","5.12.0","5.2.0","5.3.0","5.4.0","5.5.0","5.6.0","5.7.0","5.8.0","5.9.0"]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Server 16.0","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.10.0-160000.3.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Server for SAP applications 16.0","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.10.0-160000.3.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Server 16.0","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.10.0-160000.3.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Server for SAP applications 16.0","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.10.0-160000.3.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Module for Development Tools 15 SP7","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.35-150100.3.13.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Module for Package Hub 15 SP7","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.35-150100.3.13.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.35-150100.3.13.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.35-150100.3.13.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.35-150100.3.13.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.35-150100.3.13.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Server 15 SP4-LTSS","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.35-150100.3.13.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Server 15 SP5-LTSS","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.35-150100.3.13.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Server 15 SP6-LTSS","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.35-150100.3.13.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Server for SAP Applications 15 SP4","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.35-150100.3.13.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Server for SAP Applications 15 SP5","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.35-150100.3.13.1"}]}]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Server for SAP Applications 15 SP6","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.35-150100.3.13.1"}]}]},{"source":"osv","ecosystem":"Ubuntu:14.04:LTS","package":"pandas","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.12.0-2ubuntu1","0.13.1-2ubuntu1","0.13.1-2ubuntu2"]},{"source":"osv","ecosystem":"Ubuntu:16.04:LTS","package":"collada2gltf","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["20140924-3"]},{"source":"osv","ecosystem":"Ubuntu:16.04:LTS","package":"pandas","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.15.0-2","0.15.0-2ubuntu1","0.15.0-2ubuntu2","0.17.1-3ubuntu2"]},{"source":"osv","ecosystem":"Ubuntu:Pro:16.04:LTS","package":"ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.33-1","1.33-1build1","1.33-1ubuntu0.1~esm2"]},{"source":"osv","ecosystem":"Ubuntu:18.04:LTS","package":"collada2gltf","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["20140924-4"]},{"source":"osv","ecosystem":"Ubuntu:18.04:LTS","package":"pandas","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.19.2-5.1ubuntu4","0.22.0-2ubuntu1","0.22.0-3","0.22.0-4","0.22.0-4ubuntu1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:18.04:LTS","package":"ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.35-1build2","1.35-2","1.35-2ubuntu0.1~esm1"]},{"source":"osv","ecosystem":"Ubuntu:20.04:LTS","package":"pandas","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.23.3+dfsg-4ubuntu1","0.23.3+dfsg-4ubuntu5","0.23.3+dfsg-4ubuntu6","0.25.3+dfsg-4","0.25.3+dfsg-4build1","0.25.3+dfsg-7"]},{"source":"osv","ecosystem":"Ubuntu:Pro:20.04:LTS","package":"ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.35-3build1","1.35-3build2","1.35-4","1.35-4build1","1.35-4ubuntu0.1","1.35-4ubuntu0.1+esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:22.04:LTS","package":"ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.0.2-1","4.0.2-1build1","4.2.0-1","5.1.0-1","5.1.0-1build1","5.1.0-1ubuntu0.1~esm1","5.1.0-1ubuntu0.1~esm2"]},{"source":"osv","ecosystem":"Ubuntu:Pro:24.04:LTS","package":"ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.8.0-1","5.8.0-1build1","5.9.0-1","5.9.0-1build1","5.9.0-1ubuntu0.1~esm1"]},{"source":"osv","ecosystem":"Ubuntu:25.10","package":"pandas","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.2.3+dfsg-8build1","2.2.3+dfsg-9"]},{"source":"osv","ecosystem":"Ubuntu:25.10","package":"ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.10.0-1build2","5.10.0-1ubuntu0.1"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"pandas","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.3.3+dfsg-3ubuntu1","2.3.3+dfsg-3ubuntu3"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.11.0-3build1","5.13.0-1"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.10.0-1build2","5.10.0-1build3","5.11.0-3","5.11.0-3build1","5.11.0-3ubuntu0.1"]},{"source":"osv","ecosystem":"openSUSE:Leap 16.0","package":"python-ujson","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.10.0-160000.3.1"}]}]}],"products":[{"vendor":"ultrajson","product":"ultrajson"},{"vendor":"ultrajson_project","product":"ultrajson"}],"references":[{"url":"https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c38f-wx89-p2xg","tags":["x_refsource_CONFIRM","exploit","Exploit","Mitigation","Patch","Vendor Advisory","advisory","web","fix","report"]},{"url":"https://github.com/ultrajson/ultrajson/commit/82af1d0ac01d09aa40c887b460d44b9d9f4bccd9","tags":["x_refsource_MISC","Patch","fix","web","report"]},{"url":"https://github.com/ultrajson/ultrajson/releases/tag/5.12.1","tags":["x_refsource_MISC","Product","Release Notes","web","advisory","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44660","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-c38f-wx89-p2xg"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44660.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-44660","tags":["advisory"]},{"url":"https://github.com/ultrajson/ultrajson","tags":["package"]},{"url":"https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2026-3606","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-45958","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2022-31116","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2022-31117","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54911","tags":["advisory"]},{"url":"https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2026-3607","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-32875","tags":["advisory"]},{"url":"https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2026-3608","tags":["advisory"]},{"url":"https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2026-3720","tags":["advisory"]},{"url":"https://www.suse.com/support/update/announcement/2026/suse-su-202623114-1/","tags":["advisory"]},{"url":"https://bugzilla.suse.com/1270301","tags":["report"]},{"url":"https://www.suse.com/security/cve/CVE-2026-44660","tags":["web"]},{"url":"https://www.suse.com/support/update/announcement/2026/suse-su-202623136-1/","tags":["advisory"]},{"url":"https://www.suse.com/support/update/announcement/2026/suse-su-20263539-1/","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-44660","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-44660","tags":["report"]},{"url":"","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-44660","title":"UltraJSON: Memory Leak in ujson.dump() on Write Failure","description":"UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.","status":"published","published":"2026-05-27T20:42:59.83Z","modified":"2026-05-30T01:49:35.278Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"high","assessor":"cna"}],"cwes":["CWE-401"],"updated_at":"2026-11-02T13:42:49.132798Z"}],"euvd":[{"id":"EUVD-2026-32663","description":"UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.","status":"published","published":"2026-05-27T20:42:59Z","modified":"2026-05-30T01:49:35Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"high"}],"updated_at":"2026-11-02T18:20:59.967985Z"}],"ghsa":[{"id":"GHSA-c38f-wx89-p2xg","title":"UltraJSON has a Memory Leak in ujson.dump() on Write Failure","description":"### Summary\n\nWhen `ujson.dump()` writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload.\n\nCode that uses `ujson.dumps()` rather than `ujson.dump()` or only JSON load/decode methods is unaffected.\n\n### Details\n\n**Vulnerability Location:**\n- `src/ujson/python/objToJSON.c:913` - `objToJSONFile()` function start\n- `src/ujson/python/objToJSON.c:931` - Error return on write failure\n- `src/ujson/python/objToJSON.c:942` - Early return without cleanup\n \n**Root Cause:**\n\nThe `objToJSONFile()` function allocates a Python string object via `ujson_dumps_internal()`, calls the file's `write()` method, and returns early if `write()` raises an exception—but never calls `Py_DECREF(string)` on the early exit path.\n\n### PoC\n```python\nimport gc, tracemalloc, ujson\n\nclass BadFile:\n    def write(self, s):\n        raise RuntimeError(\"boom\")\n\nobj = {\"x\": \"A\" * 200000}\n\ndef run():\n    try:\n        ujson.dump(obj, BadFile())\n    except RuntimeError:\n        pass\n\nrun()\ntracemalloc.start()\ngc.collect()\nbase = tracemalloc.get_traced_memory()[0]\n\nfor i in range(5):\n    run()\n    gc.collect()\n    cur = tracemalloc.get_traced_memory()[0]\n    print(i, cur - base)\n```\n\n### Impact\n\nAny application that serializes data through `ujson.dump()` to an attacker-influenced file-like object that can fail can be driven into linear memory growth. An attacker can quickly use up all the memory of say a web server that sends JSON responses using `ujson.dump()` by repeatedly making requests then closing the connection mid response.\n\n### Remediation\n\nThe missing dec-refs were added in 82af1d0ac01d09aa40c887b460d44b9d9f4bccd9. We recommend upgrading to [UltraJSON 5.12.1](https://github.com/ultrajson/ultrajson/releases/tag/5.12.1).\n\n### Workarounds\n\nReplacing `ujson.dump(obj, file)` with `file.write(ujson.dumps(obj))` is equivalent (contrary to popular misconception, there are no streaming benefits to using `ujson.dump()`) and will avoid the memory leak.","status":"published","published":"2026-05-12T22:25:11Z","modified":"2026-06-08T23:53:58Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"high"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-401"],"updated_at":"2026-11-02T14:40:21.48274Z"}],"nvd":[{"id":"CVE-2026-44660","description":"UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.","status":"published","published":"2026-05-27T21:16:17.65Z","modified":"2026-06-17T10:51:12.35Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high","assessor":"secondary"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"primary"}],"cwes":["CWE-401"],"updated_at":"2026-11-02T14:12:20.885865Z"}],"osv":[{"id":"CVE-2026-44660","title":"UltraJSON: Memory Leak in ujson.dump() on Write Failure","description":"UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.","status":"published","published":"2026-05-27T20:42:59.83Z","modified":"2026-10-28T11:10:56.645272243Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-401"],"updated_at":"2026-11-02T15:45:05.172514Z"},{"id":"DEBIAN-CVE-2026-44660","description":"UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.","status":"published","published":"2026-05-27T21:16:17.65Z","modified":"2026-10-01T03:03:13.636459633Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:45:55.669088Z"},{"id":"GHSA-c38f-wx89-p2xg","title":"UltraJSON has a Memory Leak in ujson.dump() on Write Failure","description":"### Summary\n\nWhen `ujson.dump()` writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload.\n\nCode that uses `ujson.dumps()` rather than `ujson.dump()` or only JSON load/decode methods is unaffected.\n\n### Details\n\n**Vulnerability Location:**\n- `src/ujson/python/objToJSON.c:913` - `objToJSONFile()` function start\n- `src/ujson/python/objToJSON.c:931` - Error return on write failure\n- `src/ujson/python/objToJSON.c:942` - Early return without cleanup\n \n**Root Cause:**\n\nThe `objToJSONFile()` function allocates a Python string object via `ujson_dumps_internal()`, calls the file's `write()` method, and returns early if `write()` raises an exception—but never calls `Py_DECREF(string)` on the early exit path.\n\n### PoC\n```python\nimport gc, tracemalloc, ujson\n\nclass BadFile:\n    def write(self, s):\n        raise RuntimeError(\"boom\")\n\nobj = {\"x\": \"A\" * 200000}\n\ndef run():\n    try:\n        ujson.dump(obj, BadFile())\n    except RuntimeError:\n        pass\n\nrun()\ntracemalloc.start()\ngc.collect()\nbase = tracemalloc.get_traced_memory()[0]\n\nfor i in range(5):\n    run()\n    gc.collect()\n    cur = tracemalloc.get_traced_memory()[0]\n    print(i, cur - base)\n```\n\n### Impact\n\nAny application that serializes data through `ujson.dump()` to an attacker-influenced file-like object that can fail can be driven into linear memory growth. An attacker can quickly use up all the memory of say a web server that sends JSON responses using `ujson.dump()` by repeatedly making requests then closing the connection mid response.\n\n### Remediation\n\nThe missing dec-refs were added in 82af1d0ac01d09aa40c887b460d44b9d9f4bccd9. We recommend upgrading to [UltraJSON 5.12.1](https://github.com/ultrajson/ultrajson/releases/tag/5.12.1).\n\n### Workarounds\n\nReplacing `ujson.dump(obj, file)` with `file.write(ujson.dumps(obj))` is equivalent (contrary to popular misconception, there are no streaming benefits to using `ujson.dump()`) and will avoid the memory leak.","status":"published","published":"2026-05-12T22:25:11Z","modified":"2026-09-10T03:51:05.194201525Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"},{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-401"],"updated_at":"2026-11-02T15:46:44.571161Z"},{"id":"OESA-2026-3606","title":"python-ujson security update","description":"UltraJSON\r\n\r\nSecurity Fix(es):\n\nUltraJSON (aka ujson) through 5.1.0 has a stack-based buffer overflow in Buffer_AppendIndentUnchecked (called from encode). Exploitation can, for example, use a large amount of indentation.(CVE-2021-45958)\n\nUltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Affected versions were found to improperly decode certain characters. JSON strings that contain escaped surrogate characters not part of a proper surrogate pair were decoded incorrectly. Besides corrupting strings, this allowed for potential key confusion and value overwriting in dictionaries. All users parsing JSON from untrusted sources are vulnerable. From version 5.4.0, UltraJSON decodes lone surrogates in the same way as the standard library\u0026apos;s `json` module does, preserving them in the parsed output. Users are advised to upgrade. There are no known workarounds for this issue.(CVE-2022-31116)\n\nUltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. In versions prior to 5.4.0 an error occurring while reallocating a buffer for string decoding can cause the buffer to get freed twice. Due to how UltraJSON uses the internal decoder, this double free is impossible to trigger from Python. This issue has been resolved in version 5.4.0 and all users should upgrade to UltraJSON 5.4.0. There are no known workarounds for this issue.(CVE-2022-31117)\n\nUltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.(CVE-2026-44660)\n\nUltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.13.0, ujson.dumps() (or ujson.dump() or ujson.encode()) have a reject_bytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different Unicode characters instead of rejecting them. This leads to input validation bypass and data integrity issues. This vulnerability is fixed in 5.13.0.(CVE-2026-54911)","status":"published","published":"2026-09-05T15:03:05Z","modified":"2026-09-05T15:16:25.986617277Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:52:47.217107Z"},{"id":"OESA-2026-3607","title":"python-ujson security update","description":"UltraJSON\r\n\r\nSecurity Fix(es):\n\nUltraJSON (aka ujson) through 5.1.0 has a stack-based buffer overflow in Buffer_AppendIndentUnchecked (called from encode). Exploitation can, for example, use a large amount of indentation.(CVE-2021-45958)\n\nUltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Versions 5.10 through 5.11.0 are vulnerable to buffer overflow or infinite loop through large indent handling. ujson.dumps() crashes the Python interpreter (segmentation fault) when the product of the indent parameter and the nested depth of the input exceeds INT32_MAX. It can also get stuck in an infinite loop if the indent is a large negative number. Both are caused by an integer overflow/underflow whilst calculating how much memory to reserve for indentation. And both can be used to achieve denial of service. To be vulnerable, a service must call ujson.dump()/ujson.dumps()/ujson.encode() whilst giving untrusted users control over the indent parameter and not restrict that indentation to reasonably small non-negative values. A service may also be vulnerable to the infinite loop if it uses a fixed negative indent. An underflow always occurs for any negative indent when the input data is at least one level nested but, for small negative indents, the underflow is usually accidentally rectified by another overflow. This issue has been fixed in version 5.12.0.(CVE-2026-32875)\n\nUltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.(CVE-2026-44660)\n\nUltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.13.0, ujson.dumps() (or ujson.dump() or ujson.encode()) have a reject_bytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different Unicode characters instead of rejecting them. This leads to input validation bypass and data integrity issues. This vulnerability is fixed in 5.13.0.(CVE-2026-54911)","status":"published","published":"2026-09-05T15:03:06Z","modified":"2026-09-05T15:16:25.284263547Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:52:47.217107Z"},{"id":"OESA-2026-3608","title":"python-ujson security update","description":"UltraJSON\r\n\r\nSecurity Fix(es):\n\nUltraJSON (aka ujson) through 5.1.0 has a stack-based buffer overflow in Buffer_AppendIndentUnchecked (called from encode). Exploitation can, for example, use a large amount of indentation.(CVE-2021-45958)\n\nUltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Versions 5.10 through 5.11.0 are vulnerable to buffer overflow or infinite loop through large indent handling. ujson.dumps() crashes the Python interpreter (segmentation fault) when the product of the indent parameter and the nested depth of the input exceeds INT32_MAX. It can also get stuck in an infinite loop if the indent is a large negative number. Both are caused by an integer overflow/underflow whilst calculating how much memory to reserve for indentation. And both can be used to achieve denial of service. To be vulnerable, a service must call ujson.dump()/ujson.dumps()/ujson.encode() whilst giving untrusted users control over the indent parameter and not restrict that indentation to reasonably small non-negative values. A service may also be vulnerable to the infinite loop if it uses a fixed negative indent. An underflow always occurs for any negative indent when the input data is at least one level nested but, for small negative indents, the underflow is usually accidentally rectified by another overflow. This issue has been fixed in version 5.12.0.(CVE-2026-32875)\n\nUltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.(CVE-2026-44660)\n\nUltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.13.0, ujson.dumps() (or ujson.dump() or ujson.encode()) have a reject_bytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different Unicode characters instead of rejecting them. This leads to input validation bypass and data integrity issues. This vulnerability is fixed in 5.13.0.(CVE-2026-54911)","status":"published","published":"2026-09-05T15:03:07Z","modified":"2026-09-05T15:16:22.436261367Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:52:47.217107Z"},{"id":"OESA-2026-3720","title":"python-ujson security update","description":"UltraJSON\r\n\r\nSecurity Fix(es):\n\nUltraJSON (aka ujson) through 5.1.0 has a stack-based buffer overflow in Buffer_AppendIndentUnchecked (called from encode). Exploitation can, for example, use a large amount of indentation.(CVE-2021-45958)\n\nUltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Versions 5.10 through 5.11.0 are vulnerable to buffer overflow or infinite loop through large indent handling. ujson.dumps() crashes the Python interpreter (segmentation fault) when the product of the indent parameter and the nested depth of the input exceeds INT32_MAX. It can also get stuck in an infinite loop if the indent is a large negative number. Both are caused by an integer overflow/underflow whilst calculating how much memory to reserve for indentation. And both can be used to achieve denial of service. To be vulnerable, a service must call ujson.dump()/ujson.dumps()/ujson.encode() whilst giving untrusted users control over the indent parameter and not restrict that indentation to reasonably small non-negative values. A service may also be vulnerable to the infinite loop if it uses a fixed negative indent. An underflow always occurs for any negative indent when the input data is at least one level nested but, for small negative indents, the underflow is usually accidentally rectified by another overflow. This issue has been fixed in version 5.12.0.(CVE-2026-32875)\n\nUltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.(CVE-2026-44660)\n\nUltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.13.0, ujson.dumps() (or ujson.dump() or ujson.encode()) have a reject_bytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different Unicode characters instead of rejecting them. This leads to input validation bypass and data integrity issues. This vulnerability is fixed in 5.13.0.(CVE-2026-54911)","status":"published","published":"2026-09-14T16:33:43Z","modified":"2026-09-13T16:45:31.33071619Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:52:47.217107Z"},{"id":"PYSEC-2026-2293","description":"UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.","status":"published","published":"2026-05-27T21:16:17.65Z","modified":"2026-07-13T07:15:45.423783162Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:52:55.537808Z"},{"id":"UBUNTU-CVE-2026-44660","description":"UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.","status":"published","published":"2026-05-27T21:16:00Z","modified":"2026-11-09T12:49:51.089316499Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"high"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-09T13:27:42.046613Z"},{"id":"openSUSE-SU-2026:21518-1","title":"Security update for python-ujson","description":"This update for python-ujson fixes the following issue:\n\n- CVE-2026-44660: failing to decrement a serialized JSON object during a write exception in ujson.dump() can lead to\n  memory leaks (bsc#1270301).\n","status":"published","published":"2026-08-03T10:37:28Z","modified":"2026-08-05T18:23:52.452382336Z","updated_at":"2026-11-02T16:58:41.885092Z"},{"id":"SUSE-SU-2026:23114-1","title":"Security update for python-ujson","description":"This update for python-ujson fixes the following issue:\n\n- CVE-2026-44660: failing to decrement a serialized JSON object during a write exception in ujson.dump() can lead to\n  memory leaks (bsc#1270301).\n","status":"published","published":"2026-08-03T10:37:39Z","modified":"2026-08-14T18:23:39.766955461Z","updated_at":"2026-11-02T15:54:03.503431Z"},{"id":"SUSE-SU-2026:23136-1","title":"Security update for python-ujson","description":"This update for python-ujson fixes the following issue:\n\n- CVE-2026-44660: failing to decrement a serialized JSON object during a write exception in ujson.dump() can lead to\n  memory leaks (bsc#1270301).\n","status":"published","published":"2026-08-03T10:37:39Z","modified":"2026-08-14T18:23:45.4775258Z","updated_at":"2026-11-02T15:54:03.503431Z"},{"id":"SUSE-SU-2026:3539-1","title":"Security update for python-ujson","description":"This update for python-ujson fixes the following issue:\n\n- CVE-2026-44660: memory leak in `ujson.dump()` on write failure can lead to DoS (bsc#1270301).\n","status":"published","published":"2026-08-10T11:19:10Z","modified":"2026-08-11T09:15:07.294667588Z","updated_at":"2026-11-02T15:54:05.392906Z"}]}}