CVE-2026-27448
MEDIUMpyOpenSSL allows TLS connection bypass via unhandled callback exception in set_tlsext_servername_callback
Title source: cnaDescription
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.
References (3)
Core 3
Core References
X_Refsource_Confirm x_refsource_confirm
https://github.com/pyca/pyopenssl/security/advisories/GHSA-vp96-hxj8-p424
X_Refsource_Misc x_refsource_misc
https://github.com/pyca/pyopenssl/commit/d41a814759a9fb49584ca8ab3f7295de49a85aa0
X_Refsource_Misc x_refsource_misc
https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst#L27
Scores
CVSS v3
5.3
EPSS
0.0024
EPSS Percentile
15.0%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
no
Technical Impact
partial
Details
CWE
CWE-636
Status
published
Products (3)
pyca/pyopenssl
>= 0.14.0, < 26.0.0
pyopenssl/pyopenssl
0.14 - 26.0.0
pypi/pyopenssl
0.14.0 - 26.0.0PyPI
Published
Mar 18, 2026
Tracked Since
Mar 18, 2026