CVE-2026-27448
LOWpyOpenSSL 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.
Scores
CVSS v4
1.7
EPSS
0.0004
EPSS Percentile
12.3%
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
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
no
Technical Impact
partial
Details
CWE
CWE-636
Status
published
Products (2)
pyca/pyopenssl
>= 0.14.0, < 26.0.0
pypi/pyopenssl
0.14.0 - 26.0.0PyPI
Published
Mar 18, 2026
Tracked Since
Mar 18, 2026