CVE-2026-27448: low-severity vulnerability in pyca pyopenssl
pyOpenSSL allows TLS connection bypass via unhandled callback exception in set_tlsext_servername_callback
Published · Updated
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8Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 1.7epss 0.3%
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.
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
Affected products
pyca · pyopensslRelated CVEs — pyca pyopenssl
In the same product, most dangerous first.