CVE-2026-3644

MEDIUM

Incomplete control character validation in http.cookies

Title source: cna

Description

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().

References (6)

[Vendor Advisory] https://mail.python.org/archives/list/[email protected]/thread/H6CADMBCDRFGWCMOXWUIHFJNV43GABJ7/

[Patch] https://github.com/python/cpython/commit/57e88c1cf95e1481b94ae57abe1010469d47a6b4

View Patch ZIP pw:eip

[Issue Tracking] https://github.com/python/cpython/issues/145599

[Patch] https://github.com/python/cpython/pull/145600

[Patch] https://github.com/python/cpython/commit/62ceb396fcbe69da1ded3702de586f4072b590dd

[Patch] https://github.com/python/cpython/commit/d16ecc6c3626f0e2cc8f08c309c83934e8a979dd

Scores

CVSS v4 6.0

EPSS 0.0004

EPSS Percentile 12.8%

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N

CISA SSVC

Vulnrichment

Exploitation none

Automatable no

Technical Impact partial

Details

CWE

CWE-20 CWE-116

Status published

Products (4)

Python Software Foundation/CPython < 3.13.13

Python Software Foundation/CPython < 3.15.0

Python Software Foundation/CPython 3.14.0 - 3.14.4

Python Software Foundation/CPython 3.15.0a1 - 3.15.0a8

Published Mar 16, 2026

Tracked Since Mar 16, 2026