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Vulnerability · Published Mar 16, 2026 · Assigned by PSF

CVE-2026-3644Incomplete control character validation in http.cookies

Medium 6.0

In plain English

A medium-severity improper input validation in CPython from Python Software Foundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 44% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)6.0Medium
Exploit odds (30 days)0.5%top 56.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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().

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:10python-unversioned-command3.12.13-2.el10_2ALSA-2026:19064
AlmaLinux:10python33.12.13-2.el10_2ALSA-2026:19064
AlmaLinux:10python3-debug3.12.13-2.el10_2ALSA-2026:19064
AlmaLinux:10python3-devel3.12.13-2.el10_2ALSA-2026:19064
AlmaLinux:10python3-idle3.12.13-2.el10_2ALSA-2026:19064
AlmaLinux:10python3-libs3.12.13-2.el10_2ALSA-2026:19064
AlmaLinux:10python3-test3.12.13-2.el10_2ALSA-2026:19064
AlmaLinux:10python3-tkinter3.12.13-2.el10_2ALSA-2026:19064
AlmaLinux:8python3.123.12.13-2.el8_10ALSA-2026:10950
AlmaLinux:9python3.123.12.13-2.el9_8ALSA-2026:19177
AlmaLinux:8python3.12-debug3.12.13-2.el8_10ALSA-2026:10950
AlmaLinux:9python3.12-debug3.12.13-2.el9_8ALSA-2026:19177
AlmaLinux:8python3.12-devel3.12.13-2.el8_10ALSA-2026:10950
AlmaLinux:9python3.12-devel3.12.13-2.el9_8ALSA-2026:19177
AlmaLinux:8python3.12-idle3.12.13-2.el8_10ALSA-2026:10950
AlmaLinux:9python3.12-idle3.12.13-2.el9_8ALSA-2026:19177
AlmaLinux:8python3.12-libs3.12.13-2.el8_10ALSA-2026:10950
AlmaLinux:9python3.12-libs3.12.13-2.el9_8ALSA-2026:19177
AlmaLinux:8python3.12-rpm-macros3.12.13-2.el8_10ALSA-2026:10950
AlmaLinux:8python3.12-test3.12.13-2.el8_10ALSA-2026:10950
AlmaLinux:9python3.12-test3.12.13-2.el9_8ALSA-2026:19177
AlmaLinux:8python3.12-tkinter3.12.13-2.el8_10ALSA-2026:10950
AlmaLinux:9python3.12-tkinter3.12.13-2.el9_8ALSA-2026:19177
AlmaLinux:10python3.143.14.4-2.el10_2ALSA-2026:19019
AlmaLinux:9python3.143.14.4-2.el9_8ALSA-2026:19176
AlmaLinux:10python3.14-debug3.14.4-2.el10_2ALSA-2026:19019
AlmaLinux:9python3.14-debug3.14.4-2.el9_8ALSA-2026:19176
AlmaLinux:10python3.14-devel3.14.4-2.el10_2ALSA-2026:19019
AlmaLinux:9python3.14-devel3.14.4-2.el9_8ALSA-2026:19176
AlmaLinux:10python3.14-freethreading3.14.4-2.el10_2ALSA-2026:19019
AlmaLinux:9python3.14-freethreading3.14.4-2.el9_8ALSA-2026:19176
AlmaLinux:10python3.14-freethreading-debug3.14.4-2.el10_2ALSA-2026:19019
AlmaLinux:9python3.14-freethreading-debug3.14.4-2.el9_8ALSA-2026:19176
AlmaLinux:10python3.14-freethreading-devel3.14.4-2.el10_2ALSA-2026:19019
AlmaLinux:9python3.14-freethreading-devel3.14.4-2.el9_8ALSA-2026:19176
AlmaLinux:10python3.14-freethreading-idle3.14.4-2.el10_2ALSA-2026:19019
AlmaLinux:9python3.14-freethreading-idle3.14.4-2.el9_8ALSA-2026:19176
AlmaLinux:10python3.14-freethreading-libs3.14.4-2.el10_2ALSA-2026:19019
AlmaLinux:9python3.14-freethreading-libs3.14.4-2.el9_8ALSA-2026:19176
AlmaLinux:10python3.14-freethreading-test3.14.4-2.el10_2ALSA-2026:19019
AlmaLinux:9python3.14-freethreading-test3.14.4-2.el9_8ALSA-2026:19176
AlmaLinux:10python3.14-freethreading-tkinter3.14.4-2.el10_2ALSA-2026:19019
AlmaLinux:9python3.14-freethreading-tkinter3.14.4-2.el9_8ALSA-2026:19176
AlmaLinux:10python3.14-idle3.14.4-2.el10_2ALSA-2026:19019
AlmaLinux:9python3.14-idle3.14.4-2.el9_8ALSA-2026:19176
AlmaLinux:10python3.14-libs3.14.4-2.el10_2ALSA-2026:19019
AlmaLinux:9python3.14-libs3.14.4-2.el9_8ALSA-2026:19176
AlmaLinux:10python3.14-test3.14.4-2.el10_2ALSA-2026:19019
AlmaLinux:9python3.14-test3.14.4-2.el9_8ALSA-2026:19176
AlmaLinux:10python3.14-tkinter3.14.4-2.el10_2ALSA-2026:19019
AlmaLinux:9python3.14-tkinter3.14.4-2.el9_8ALSA-2026:19176
Alpine:v3.21python33.12.14-r0ALPINE-CVE-2026-3644
Alpine:v3.22python33.12.14-r0ALPINE-CVE-2026-3644
Alpine:v3.23python33.12.14-r0ALPINE-CVE-2026-3644
Alpine:v3.24python33.14.5-r0ALPINE-CVE-2026-3644
Debian:12python3.113.11.2-6+deb12u8DEBIAN-CVE-2026-3644
Debian:13python3.133.13.5-2+deb13u2DEBIAN-CVE-2026-3644
Debian:14python3.143.14.3-4DEBIAN-CVE-2026-3644
Rocky Linux:10python3.120:3.12.13-2.el10_2RLSA-2026:19064
Rocky Linux:8python3.120:3.12.13-2.el8_10RLSA-2026:10950
Rocky Linux:9python3.120:3.12.13-2.el9_8RLSA-2026:19177
Rocky Linux:10python3.140:3.14.4-2.el10_2RLSA-2026:19019
Rocky Linux:9python3.140:3.14.4-2.el9_8RLSA-2026:19176
Ubuntu:22.04:LTSpython3.103.10.12-1~22.04.16USN-8509-1
Ubuntu:22.04:LTSpython3.103.10.12-1~22.04.18USN-8744-1
Ubuntu:22.04:LTSpython3.103.10.12-1~22.04.16UBUNTU-CVE-2026-3644
Ubuntu:24.04:LTSpython3.123.12.3-1ubuntu0.15UBUNTU-CVE-2026-3644
Ubuntu:24.04:LTSpython3.123.12.3-1ubuntu0.15USN-8509-1
Ubuntu:24.04:LTSpython3.123.12.3-1ubuntu0.17USN-8744-1
Ubuntu:25.10python3.13no fix listedUBUNTU-CVE-2026-3644
Ubuntu:25.10python3.14no fix listedUBUNTU-CVE-2026-3644
Ubuntu:26.04:LTSpython3.143.14.4-1ubuntu0.1USN-8509-1
Ubuntu:26.04:LTSpython3.143.14.4-1ubuntu0.2USN-8744-1

Affected products (as reported)

VendorProductVersions
Python Software Foundation CPython 0 – before 3.10.213.11.0 – before 3.11.163.12.0 – before 3.12.143.13.0 – before 3.13.133.14.0 – before 3.14.43.15.0a1 – before 3.15.0a8

Weakness: CWE-20, CWE-116 · Vector: 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

References