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CVE-2026-124249VulnerabilityPublished

http.cookiejar.CookieJar deleted a stored cookie when a response carried an already expired Set-Cookie header for it

Source GCVE Database

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Authoritative record:CVE-2026-124249· Medium 6.3

Not known to be exploited · CVSS 6.3 Medium : upgrade to 3.16.0 when convenient.

Data as of 9 Nov 2026, 16:36 UTC

CVSS 4.0 base score
6.3Medium
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (PSF)CVSS 4.06.3
Patch
Available – fixed in 3.16.0
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 9 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 9 Nov 2026.

What to do

Upgrade CPython to 3.16.0.

Affected software

ProductAffectedFixed in
Python Software FoundationCPythonAffected
  • <3.16.0
Fixed in
  • 3.16.0
GitHubCPythonpkg:github/CPythonOther threatsAffected
  • <3.16.0
Fixed in
  • 3.16.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available that ensures the cookie policy is consulted before an expired cookie can delete an existing one, as required by RFC 6265 section 5.3. Users should update to the fixed version once available.

Description

The http.cookiejar.CookieJar component improperly deleted stored cookies when receiving a response with an already expired Set-Cookie header. This deletion occurred without consulting the cookie policy, allowing a server to potentially delete cookies from other domains within a shared cookie jar, such as urllib's HTTPCookieProcessor. The issue was fixed by ensuring the cookie policy is checked before allowing an expired cookie to delete an existing one, in compliance with RFC 6265 section 5.3.

References

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