Null Byte Vulnerability in Python's Socket Library
CVE-2026-116566

5.3MEDIUM

Key Information:

Vendor

Python Software Foundation

Status
Cpython
Vendor
CVE Published:
29 October 2026

What is CVE-2026-116566?

The vulnerability in Python's socket.getaddrinfo() function allowed null bytes within the host and port parameters. This misuse could lead to unintended behavior, where the specified values were silently truncated. Affected versions failed to adequately sanitize input, potentially resulting in incorrect socket behavior and associated risks. To mitigate this, users should update to the latest version where this issue has been addressed.

Affected Version(s)

CPython 0 < 3.16.0

References

https://github.com/python/cpython/pull/160899
patch
https://github.com/python/cpython/issues/160898
issue-tracking
https://mail.python.org/archives/list/security-announce@p...
vendor-advisory

CVSS V4

Score:
5.3
Severity:
MEDIUM
Confidentiality:
High
Integrity:
High
Availability:
None
Attack Vector:
Adjacent Network
Attack Complexity:
Low
Attack Required:
Physical
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Venukamatchi (https://github.com/Venukamatchi)
Seth Larson (https://github.com/sethmlarson)
Gregory P. Smith (https://github.com/gpshead)
Stan Ulbrych (https://github.com/StanFromIreland)
.