CVE-2026-27448

pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 0.14.0 and prior to version 26.0.0, 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. Starting in version 26.0.0, unhandled exceptions now result in rejecting the connection.

Score

CVSS 3.1 5.3 Medium

Status

Analyzed - security-advisories@github.com

Published

2026-03-18

Last modified

2026-03-18

Weaknesses

CWE-636

Affected products

• Pyopenssl (Pyca)
• Pyopenssl (Pyopenssl)

References

• https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst#L27
• https://github.com/pyca/pyopenssl/commit/d41a814759a9fb49584ca8ab3f7295de49a85aa0
• https://github.com/pyca/pyopenssl/security/advisories/GHSA-vp96-hxj8-p424