GitHub Advisoryadvisory · PyPI

GHSA-vp96-hxj8-p424 pyOpenSSL allows TLS connection bypass via unhandled callback exception in set_tlsext_servername_callback

LOW Published 2026-03-16 Modified 2026-03-19 Official page ↗
Aliases
CVE-2026-27448
Ecosystem
PyPI
Packages
pyopenssl
Severity
Low
CVSS vector
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U
Weaknesses
CWE-636
Reviewed
2026-03-16

Affected packages

• PyPI pyopenssl: >= 0.14.0, < 26.0.0 → fixed in 26.0.0

Description

If a user provided callback to `set_tlsext_servername_callback` raised an unhandled exception, this would result in a connection being accepted. If a user was relying on this callback for any security-sensitive behavior, this could allow bypassing it. Unhandled exceptions now result in rejecting the connection. Credit to Leury Castillo for reporting this issue.

Related

Alias · CVE (1)

  • CVE-2026-27448 pyOpenSSL is a Python wrapper around the OpenSSL library. vulnerability

Weakness · CWE (1)

  • CWE-636 Not Failing Securely weakness

References