CVE-2026-6019

MEDIUM

BaseCookie.js_output() does not neutralize embedded characters

Title source: cna

Description

http.cookies.Morsel.js_output() returns an inline <script> snippet and only escapes " for JavaScript string context. It does not neutralize the HTML parser-sensitive sequence </script> inside the generated script element. Mitigation base64-encodes the cookie value to disallow escaping using cookie value.

References (6)

Core 6

Core References

Patch patch

https://github.com/python/cpython/commit/3c59b8b53fc75c7f9578d16fb8201ceb43e8f76c

View Patch ZIP pw:eip

Patch patch

https://github.com/python/cpython/commit/f795e042043dfe26c42e1971d4502c1cdc4c65b8

View Patch ZIP pw:eip

Patch patch

https://github.com/python/cpython/pull/148848

Issue Tracking issue-tracking

https://github.com/python/cpython/issues/90309

Vendor Advisory vendor-advisory

https://mail.python.org/archives/list/[email protected]/thread/IVNWGV2BBNC3RHQAFS22UP4DY56SAXX3/

Patch patch

https://github.com/python/cpython/commit/76b3923d688c0efc580658476c5f525ec8735104

View Patch ZIP pw:eip

Scores

CVSS v3 6.1

EPSS 0.0023

EPSS Percentile 13.5%

Attack Vector NETWORK

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CISA SSVC

Vulnrichment

Exploitation none

Automatable no

Technical Impact partial

Details

CWE

CWE-116 CWE-150

Status published

Products (6)

python/cpython < 3.15.0

python/python < 3.15.0

Python Software Foundation/CPython < 3.13.14

Python Software Foundation/CPython < 3.15.0

Python Software Foundation/CPython 3.14.0a1 - 3.14.5rc1

Python Software Foundation/CPython 3.15.0a1 - 3.15.0b1

Published Apr 22, 2026

Tracked Since Apr 23, 2026