HTTP Client Proxy Tunnel Header Vulnerability in Python Software Foundation's CPython
CVE-2026-1502

5.7MEDIUM

Key Information:

Vendor

Python Software Foundation

Status
Cpython
Vendor
CVE Published:
10 April 2026

What is CVE-2026-1502?

This vulnerability allows an attacker to manipulate CR/LF bytes in HTTP client proxy tunnel headers or host, potentially leading to HTTP request smuggling or other unintended behaviors. Proper validation was missing, enabling exploitation of the system. A patch has been implemented, ensuring that such malicious bytes are effectively rejected, enhancing the security of CPython.

Affected Version(s)

CPython 0 < 3.15.0

References

https://github.com/python/cpython/pull/146212
patch
https://github.com/python/cpython/issues/146211
issue-tracking
https://mail.python.org/archives/list/security-announce@p...
vendor-advisory

CVSS V4

Score:
5.7
Severity:
MEDIUM
Confidentiality:
None
Integrity:
High
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
Physical
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

senseicat
Seth Larson
.