{"id":"CVE-2023-6936","aliases":["DEBIAN-CVE-2023-6936","EUVD-2023-59134","GHSA-cwpg-8775-j56v","JLSEC-2026-678","UBUNTU-CVE-2023-6936"],"status":"published","title":"Heap-buffer over-read with WOLFSSL_CALLBACKS","description":"In wolfSSL prior to 5.6.6, if callback functions are enabled (via the WOLFSSL_CALLBACKS flag), then a malicious TLS client or network attacker can trigger a buffer over-read on the heap of 5 bytes (WOLFSSL_CALLBACKS is only intended for debugging).","severity":{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.006,"percentile":0.49235,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-125","CWE-126"],"published":"2024-02-20T21:52:02Z","modified":"2026-10-28T02:31:11Z","fixes":[{"ecosystem":"Debian:13","package":"wolfssl","fixed_in":["5.6.6-1.2"],"sources":["osv"]},{"ecosystem":"Julia","package":"wolfSSL_jll","fixed_in":["5.7.2+0"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Debian:12","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.5.4-2","5.5.4-2+deb12u1","5.5.4-2+deb12u2","5.5.4-2+deb12u3","5.5.4-2.1","5.6.4-1","5.6.4-2","5.6.6-1","5.6.6-1.1","5.6.6-1.2","5.6.6-1.3","5.6.6-1.3~exp1","5.7.0-0.1","5.7.0-0.2","5.7.0-0.3","5.7.2-0.1","5.7.2-0.2","5.7.2-0.3","5.7.2-0.4","5.8.2-1","5.8.2-1.1","5.8.2-1.2","5.8.4-1","5.9.0-0.1","5.9.0-0.2","5.9.1-0.1","5.9.2-1","5.9.2-1.1","5.9.2-1.2"]},{"source":"osv","ecosystem":"Debian:13","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.6.6-1.2"}]}]},{"source":"osv","ecosystem":"Julia","package":"wolfSSL_jll","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"5.7.2+0"}]}]},{"source":"osv","ecosystem":"Ubuntu:16.04:LTS","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.4.8+dfsg-1"]},{"source":"osv","ecosystem":"Ubuntu:18.04:LTS","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.10.2+dfsg-2","3.12.0+dfsg-1","3.12.2+dfsg-1","3.13.0+dfsg-1"]},{"source":"osv","ecosystem":"Ubuntu:20.04:LTS","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.1.0+dfsg-2","4.2.0+dfsg-1","4.2.0+dfsg-2","4.2.0+dfsg-3","4.3.0+dfsg-2"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"wolfssl","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.6.0-3","5.0.0-1","5.1.1-1","5.2.0-1","5.2.0-2"]}],"products":[{"vendor":"wolfssl","product":"wolfssl"}],"references":[{"url":"https://github.com/wolfSSL/wolfssl/pull/6949/","tags":["patch","x_transferred","Issue Tracking","Patch","fix","web"]},{"url":"https://www.wolfssl.com/docs/security-vulnerabilities/","tags":["vendor-advisory","x_transferred","Vendor Advisory","advisory","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2023-6936","tags":["advisory","web"]},{"url":"https://github.com/wolfSSL/wolfssl/pull/6949","tags":["web"]},{"url":"https://www.wolfssl.com/docs/security-vulnerabilities","tags":["web"]},{"url":"https://github.com/advisories/GHSA-cwpg-8775-j56v","tags":["web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/6xxx/CVE-2023-6936.json","tags":["advisory"]},{"url":"https://github.com/wolfSSL/wolfssl","tags":["package"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2023-6936","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2023-6936","tags":["report"]},{"url":"https://github.com/wolfSSL/wolfssl/blob/v5.6.6-stable/ChangeLog.md#vulnerabilities","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2023-6936","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2023-6936","title":" Heap-buffer over-read with WOLFSSL_CALLBACKS","description":"In wolfSSL prior to 5.6.6, if callback functions are enabled (via the WOLFSSL_CALLBACKS flag), then a malicious TLS client or network attacker can trigger a buffer over-read on the heap of 5 bytes (WOLFSSL_CALLBACKS is only intended for debugging).\n","status":"published","published":"2024-02-20T21:52:02.441Z","modified":"2025-03-26T16:28:30.322Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-126"],"updated_at":"2026-11-02T14:35:25.469654Z"}],"euvd":[{"id":"EUVD-2023-59134","description":"In wolfSSL prior to 5.6.6, if callback functions are enabled (via the WOLFSSL_CALLBACKS flag), then a malicious TLS client or network attacker can trigger a buffer over-read on the heap of 5 bytes (WOLFSSL_CALLBACKS is only intended for debugging).\n","status":"published","published":"2024-02-20T21:52:02Z","modified":"2025-03-26T16:28:30Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium"}],"updated_at":"2026-11-02T20:52:50.922534Z"}],"ghsa":[{"id":"GHSA-cwpg-8775-j56v","title":"In wolfSSL prior to 5.6.6, if callback functions are enabled (via the WOLFSSL_CALLBACKS flag),...","description":"In wolfSSL prior to 5.6.6, if callback functions are enabled (via the WOLFSSL_CALLBACKS flag), then a malicious TLS client or network attacker can trigger a buffer over-read on the heap of 5 bytes (WOLFSSL_CALLBACKS is only intended for debugging).","status":"published","published":"2024-02-21T00:31:31Z","modified":"2025-03-26T18:31:48Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium"}],"cwes":["CWE-125","CWE-126"],"updated_at":"2026-11-02T15:00:28.149554Z"}],"nvd":[{"id":"CVE-2023-6936","description":"In wolfSSL prior to 5.6.6, if callback functions are enabled (via the WOLFSSL_CALLBACKS flag), then a malicious TLS client or network attacker can trigger a buffer over-read on the heap of 5 bytes (WOLFSSL_CALLBACKS is only intended for debugging).\n","status":"published","published":"2024-02-20T22:15:08.197Z","modified":"2026-06-17T06:51:43.16Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium","assessor":"secondary"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","level":"critical","assessor":"primary"}],"cwes":["CWE-125","CWE-126"],"updated_at":"2026-11-02T14:09:07.077422Z"}],"osv":[{"id":"CVE-2023-6936","title":" Heap-buffer over-read with WOLFSSL_CALLBACKS","description":"In wolfSSL prior to 5.6.6, if callback functions are enabled (via the WOLFSSL_CALLBACKS flag), then a malicious TLS client or network attacker can trigger a buffer over-read on the heap of 5 bytes (WOLFSSL_CALLBACKS is only intended for debugging).\n","status":"published","published":"2024-02-20T21:52:02.441Z","modified":"2026-10-28T02:31:11.562973204Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium"}],"updated_at":"2026-11-02T15:44:37.180532Z"},{"id":"DEBIAN-CVE-2023-6936","description":"In wolfSSL prior to 5.6.6, if callback functions are enabled (via the WOLFSSL_CALLBACKS flag), then a malicious TLS client or network attacker can trigger a buffer over-read on the heap of 5 bytes (WOLFSSL_CALLBACKS is only intended for debugging).","status":"published","published":"2024-02-20T22:15:08.197Z","modified":"2026-10-26T18:01:31.72233592Z","cvss":[{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","level":"critical"}],"updated_at":"2026-11-02T15:45:41.533064Z"},{"id":"JLSEC-2026-678","title":"In wolfSSL prior to 5.6.6, if callback functions are enabled (via the `WOLFSSL_CALLBACKS` flag),...","description":"In wolfSSL prior to 5.6.6, if callback functions are enabled (via the `WOLFSSL_CALLBACKS` flag), then a malicious TLS client or network attacker can trigger a buffer over-read on the heap of 5 bytes (`WOLFSSL_CALLBACKS` is only intended for debugging).","status":"published","published":"2026-07-14T21:41:35.775Z","modified":"2026-07-25T18:23:59.54320386Z","cvss":[{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","level":"critical"}],"updated_at":"2026-11-02T15:47:19.003546Z"},{"id":"UBUNTU-CVE-2023-6936","description":"In wolfSSL prior to 5.6.6, if callback functions are enabled (via the WOLFSSL_CALLBACKS flag), then a malicious TLS client or network attacker can trigger a buffer over-read on the heap of 5 bytes (WOLFSSL_CALLBACKS is only intended for debugging).","status":"published","published":"2024-02-20T22:15:00Z","modified":"2026-04-22T14:36:35.915979Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","level":"medium"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","level":"critical"}],"updated_at":"2026-11-02T16:54:41.555387Z"}]}}