CVE-2026-16052

Cookie Attribute Injection via Unescaped Semicolons in http.cookies.Morsel

Low 2.3

Description

The http.cookies.Morsel class allows separator semicolons in attribute values and includes them verbatim in all output formats. An attacker who can control these values could use this to relax the cookie's Domain or SameSite restrictions.

Key facts

Published: 12 Nov 2026
Last changed: 12 Nov 2026
Assigned by: PSF
EPSS: 0.305% likely to be exploited in the next 30 days, higher than 23.558% of CVEs (scores for 15 Nov 2026)

Severity scores

Each score is shown as its source gave it. They are not averaged or merged.

2.3CVSS 4.0, Lowfrom the CNA (PSF)CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Historical context and remediation

This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.

No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.

No explicit remediation statement is available on this page yet. Consult the original record and vendor references before choosing a fix.

Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.

Read the original CVE record.

Affected products

Vendor	Product	Versions
Python Software Foundation	CPython	Default status: unaffected 0 up to but excluding 3.16.0 (affected)