REDHAT-BUG-2487740: High severity npm/js-cookie vulnerability
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
js-cookieto a version that resolves this vulnerability.Fixed in 3.0.7
Event History
Frequently Asked Questions
What is the severity of REDHAT-BUG-2487740?
The severity of REDHAT-BUG-2487740 is classified as high with a score of 7.
How do I fix REDHAT-BUG-2487740?
To fix REDHAT-BUG-2487740, update js-cookie to version 3.0.7 or later.
What type of vulnerability is REDHAT-BUG-2487740?
REDHAT-BUG-2487740 is a client-side JavaScript vulnerability related to cookie handling.
What software is affected by REDHAT-BUG-2487740?
The affected software is npm/js-cookie prior to version 3.0.7.
When was REDHAT-BUG-2487740 published?
REDHAT-BUG-2487740 was published on June 10, 2026.