Cross-Site Scripting Vulnerability in Python's Cookie Handling
CVE-2026-6019

2.1LOW

Key Information:

Vendor

Python Software Foundation

Status
Cpython
Vendor
CVE Published:
22 April 2026

What is CVE-2026-6019?

A vulnerability in the http.cookies.Morsel.js_output() function of Python's CPython allows attackers to inject malicious scripts through cookie data. The method does not adequately escape HTML-sensitive sequences, leading to potential cross-site scripting (XSS) attacks. Although the base64 encoding of cookie values can mitigate the risk, users should ensure they are using the latest patches to secure their applications against this threat.

Affected Version(s)

CPython 0 < 3.15.0

References

https://github.com/python/cpython/pull/148848
patch
https://github.com/python/cpython/issues/90309
issue-tracking
https://mail.python.org/archives/list/security-announce@p...
vendor-advisory

CVSS V4

Score:
2.1
Severity:
LOW
Confidentiality:
Low
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
Physical
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

oolongeya (https://github.com/komi22)
Seth Larson (https://github.com/sethmlarson)
.