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

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.

Data: CVE.org, NVD, CISA KEV, FIRST EPSS, Ubuntu. Published as the sources state it, in English.

Affected products and versions

References and patches

• https://github.com/python/cpython/pull/161570 patch
• https://github.com/python/cpython/issues/161569 issue-tracking
• https://mail.python.org/archives/list/security-announce@python.org/thread/Y6IKNZ2VZUS2L6CLQICSFUEMCLT7OLTY/ vendor-advisory
• https://github.com/python/cpython/commit/4e9d037f1cfc8e29efcb1f67bc668e06ff2b6643 patch
• https://github.com/python/cpython/commit/8eb3d2c1c41ca7ce628554413981c1eb763a1494 patch
• https://github.com/python/cpython/commit/ac1d49f4fbb33941475c5aa3cb663ab39d64cb73 patch
• http://www.openwall.com/lists/oss-security/2026/11/09/24