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CVE-2026-124249— `http.cookiejar` applies expired `Set-Cookie` to cookie store before policy validation

Quick assessment

Affected
Python Software Foundation CPython
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在收到包含已过期 头的响应时，会直接使用该头中的 和 属性删除已存储的对应 cookie，而未经过 cookie 策略检查。因此，攻击者服务器可能利用共享 cookie 存储（例如 的 所使用的存储）删除属于其他域的 cookie。修复方案是在允许已过期 cookie 删除现有 cookie 之前，先进行 cookie 策略验证，以符合 RFC 6265 第 5.3 节的要求。

CVSS 6.3 · Medium

Affected Version Matrix 1

VendorProduct Version RangeStatus
Python Software Foundation CPython < 3.16.0 affected
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I. Basic Information for CVE-2026-124249

Vulnerability Information
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Vulnerability Title
`http.cookiejar` applies expired `Set-Cookie` to cookie store before policy validation
Source: CVE Program / CVE List V5
Vulnerability Description
http.cookiejar.CookieJar deleted a stored cookie when a response carried an already expired Set-Cookie header for it, using the Domain and Path attributes from the header without consulting the cookie policy. A server could therefore delete cookies belonging to other domains from a shared cookie jar, such as the one used by urllib's HTTPCookieProcessor. The fix consults the cookie policy before an expired cookie may delete an existing one, as required by RFC 6265 section 5.3.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
源验证错误
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Python Software Foundation CPython 0 ~ 3.16.0 -

II. Public POCs for CVE-2026-124249

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III. Intelligence Information for CVE-2026-124249

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Patches & Fixes for CVE-2026-124249 (2)

Vendor Advisories for CVE-2026-124249 (1)

Mailing List Discussions for CVE-2026-124249 (1)

IV. Related Vulnerabilities

Same product: CPython
Same vendor: Python Software Foundation
Same weakness: CWE-346