High severity · published Mar 16, 2026
CVE-2026-3644
Incomplete control character validation in http.cookies
7.5
CVSS
0.5%
EPSS
No
On KEV
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().
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 42% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CP
CPython · Python Software Foundation
before 3.10.21; 3.11.0 before 3.11.16; 3.12.0 before 3.12.14; 3.13.0 before 3.13.13; 3.14.0 before 3.14.4; 3.15.0a1 before 3.15.0a8 · source: vendor
PY
Python · Python
before 3.13.13; 3.14.0 before 3.14.4; 3.15.0; 3.15.0; 3.15.0; 3.15.0; +3 more · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-3644
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-3644
github.com
https://github.com/python/cpython/commit/3974092b037f9a3b000fb15b48ea61ce3b25d330
github.com
https://github.com/python/cpython/commit/556aa098e738b127c714866f819b4abe2f7593d8
Patch
https://github.com/python/cpython/commit/57e88c1cf95e1481b94ae57abe1010469d47a6b4
Patch
https://github.com/python/cpython/commit/62ceb396fcbe69da1ded3702de586f4072b590dd
Patch
https://github.com/python/cpython/commit/d16ecc6c3626f0e2cc8f08c309c83934e8a979dd
github.com
https://github.com/python/cpython/commit/dae4b1a21f8df4570e30986affd61bbe4ade4cef
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