CVE-2026-46625
The result is a per-instance prototype hijack: Object.prototype itself is untouched, but the merged attributes object now inherits attacker-controlled keys.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.92%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- EPSS
- 0.92% probability · 58th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-1321, CWE-915
- Affected
- js-cookie/javascript cookie · redhat/3scale api management · redhat/ansible automation platform · redhat/openshift ai · redhat/openshift lightspeed · redhat/enterprise linux
- Source
- security-advisories@github.com
References
- https://github.com/js-cookie/js-cookie/commit/eb3c40e89731e99b8970faaf35ddad249c6c0020Patch
- https://github.com/js-cookie/js-cookie/releases/tag/v3.0.7Release Notes
- https://github.com/js-cookie/js-cookie/security/advisories/GHSA-qjx8-664m-686jExploit, Vendor Advisory
- https://access.redhat.com/errata/RHSA-2026:33183Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:36625Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:48126Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:48151Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:49642Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:52768Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:56338Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:56357Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:59153Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:60520
- https://access.redhat.com/security/cve/CVE-2026-46625Third Party Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2487740Issue Tracking, Third Party Advisory
- https://github.com/js-cookie/js-cookie/security/advisories/GHSA-qjx8-664m-686jExploit, Vendor Advisory
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-46625.jsonThird Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.