CVE-2026-3644 MEDIUM

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

Vendor Python Software Foundation
Product CPython
Published March 16, 2026
Last update June 30, 2026
View on NVD All CVEs

CVSS base score

6.0/10
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction None
Confidentiality —
Integrity —

CVSS 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

What the vulnerability does

01Description

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().

Key dates

02Disclosure timeline

March 16, 2026 CVE published
June 30, 2026 Record updated