CVE-2026-46625— JavaScript Cookie: Per-instance prototype hijack in assign() enables cookie-attribute injection

JavaScript Cookie: Per-instance prototype hijack in assign() enables cookie-attribute injection

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/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CWE-1321

JavaScript Cookie 安全漏洞

JavaScript Cookie是js-cookie开源的一个轻量级JavaScript Cookie操作库。 JavaScript Cookie 3.0.7之前版本存在安全漏洞，该漏洞源于内部assign()辅助函数使用for...in和普通赋值复制属性，当源对象由JSON.parse产生时，__proto__成员作为自有可枚举属性导致原型污染，攻击者可设置cookie属性。

N/A

N/A