Inconsistent interpretation of HTTP requests in Python - CVE-2026-0865
Published: February 13, 2026
Vulnerability identifier: #VU122815
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:U/U:Green
CVE-ID: CVE-2026-0865
CWE-ID: CWE-444
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Python.org
Affected software:
Python
Python
Detailed vulnerability description
The vulnerability allows a remote attacker to perform HTTP request smuggling attacks.
The vulnerability exists due to improper validation of HTTP requests. A remote attacker can send a specially crafted HTTP request to the application and smuggle arbitrary HTTP headers.
Successful exploitation of vulnerability may allow an attacker to poison HTTP cache and perform phishing attacks.
How to mitigate CVE-2026-0865
Install updates from vendor's website.
Sources
- https://github.com/python/cpython/commit/22e4d55285cee52bc4dbe061324e5f30bd4dee58
- https://github.com/python/cpython/commit/23e3c0ae867cca0130e441e776c9955b9027c510
- https://github.com/python/cpython/commit/2f840249550e082dc351743f474ba56da10478d2
- https://github.com/python/cpython/commit/4802b96a2cde58570c24c13ef3289490980961c5
- https://github.com/python/cpython/commit/e4846a93ac07a8ae9aa18203af0dd13d6e7a6995
- https://github.com/python/cpython/commit/f7fceed79ca1bceae8dbe5ba5bc8928564da7211
- https://github.com/python/cpython/issues/143916
- https://github.com/python/cpython/pull/143917
- https://mail.python.org/archives/list/security-announce@python.org/thread/BJ6QPHNSHJTS3A7CFV6IBMCAP2DWRVNT/