CVE-2026-3644

HIGH severity · CVSS 7.5 · Improper input validation

7.5CVSS HIGH

Summary

The fix for CVE-2026-0672, which rejected control characters in http.cookies.Morsel, was incomplete. The Morsel.update(), |= operator, and unpickling paths were not patched, allowing control characters to bypass input validation. Additionally, BaseCookie.js_output() lacked the output validation applied to BaseCookie.output().

Impact & exploitability

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

Confidentiality impactNone

Integrity impactHigh

Availability impactNone

Exploit probability (EPSS)0%

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected products we track (1)

Python

Recommendation

Apply the vendor fix promptly. Open any affected product above for its exact safe version.

Official patch: https://github.com/python/cpython/commit/57e88c1cf95e1481b94ae57abe1010469d47a6b4 ↗

Additional information

NVD record
https://github.com/python/cpython/commit/57e88c1cf95e1481b94ae57abe1010469d47a6b4Patch
https://github.com/python/cpython/commit/62ceb396fcbe69da1ded3702de586f4072b590ddPatch
https://github.com/python/cpython/commit/d16ecc6c3626f0e2cc8f08c309c83934e8a979ddPatch
https://github.com/python/cpython/pull/145600Patch
https://github.com/python/cpython/issues/145599
https://mail.python.org/archives/list/security-announce@python.org/thread/H6CADMBCDRFGWCMOXWUIHFJNV43GABJ7/Advisory