{"id":"CVE-2026-46625","aliases":["GHSA-qjx8-664m-686j"],"url":"https://o3.security/vulnerability/CVE-2026-46625","summary":"JavaScript Cookie: Per-instance prototype hijack in assign() enables cookie-attribute injection","details":"JavaScript Cookie is a JavaScript API for handling cookies, client-side. Prior to version 3.0.7, js-cookie's internal assign() helper copies properties with for...in + plain assignment. When the source object is produced by JSON.parse, the JSON object's \"__proto__\" member is an own enumerable property, so the for…in enumerates it and the target[key] = source[key] write triggers the Object.prototype.__proto__ setter on the fresh target ({}). The result is a per-instance prototype hijack: Object.prototype itself is untouched, but the merged attributes object now inherits attacker-controlled keys. Because the consuming set() function then enumerates the merged object with another for...in, every key the attacker placed on the polluted prototype lands in the resulting Set-Cookie string as an attribute pair. The attacker can set domain=, secure=, samesite=, expires=, and path= on cookies whose attributes the developer thought were locked down. This issue has been patched in version 3.0.7.","published":"2026-06-10T21:18:05.372Z","modified":"2026-08-12T03:51:18.574533033Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"},"epss":{"score":0.00512,"percentile":0.40884,"asOf":"2026-08-10"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"js-cookie","fixedVersion":"3.0.7"}],"fix":{"url":"https://github.com/js-cookie/js-cookie/commit/eb3c40e89731e99b8970faaf35ddad249c6c0020","label":"js-cookie/js-cookie@eb3c40e"},"references":[{"type":"WEB","url":"https://github.com/js-cookie/js-cookie/releases/tag/v3.0.7"},{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-46625.json"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:33183"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:36625"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:48126"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:48151"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:49642"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:52768"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-46625"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46625.json"},{"type":"ADVISORY","url":"https://github.com/js-cookie/js-cookie/security/advisories/GHSA-qjx8-664m-686j"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-46625"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2487740"},{"type":"FIX","url":"https://github.com/js-cookie/js-cookie/commit/eb3c40e89731e99b8970faaf35ddad249c6c0020"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:18.574533033Z"}}