CVE-2026-3644

—1

CVSS 4.0

6.0 medium

EPSS

<1%p40

Published

Mar 16, 2026 (Mar 16, 2026)

Modified

Aug 13, 2026

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().

Vendors: python
Products: python
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

NVD CVE.org GitHub PoCs EPSS (0.5%)

In the news1 stories

USN-8744-1: Python vulnerabilities

Ubuntu issued USN-8744-1 fixing CVE-2026-3644, a Python http.cookies content-injection flaw, plus a pyexpat recursion DoS across six Ubuntu LTS releases.

Ubuntu published security notice USN-8744-1 addressing two Python vulnerabilities affecting Ubuntu 14.04 LTS through 24.04 LTS. CVE-2026-3644 concerns incorrect handling of control characters in the http.cookies module, which could allow an attacker to inject arbitrary content. The second issue involves unbounded recursion in the Expat XML parser reached via the pyexpat module, which could crash Python and cause a denial of service. Updated packages are available; no exploitation in the wild is reported.

Ubuntu Security NoticesSep 10, 13:53 UTC · 5d agoAdvisory CVE-2026-36441