CVE-2026-27448 (GCVE-0-2026-27448)
Vulnerability from cvelistv5 – Published: 2026-03-17 23:24 – Updated: 2026-03-18 20:18
VLAI
EPSS
VEX
Title
pyOpenSSL allows TLS connection bypass via unhandled callback exception in set_tlsext_servername_callback
Summary
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.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-03-18 20:17 UTC
CWE
- CWE-636 - Not Failing Securely ('Failing Open')
Assigner
References
3 references
| URL | Tags |
|---|---|
| https://github.com/pyca/pyopenssl/security/adviso… | x_refsource_CONFIRM |
| https://github.com/pyca/pyopenssl/commit/d41a8147… | x_refsource_MISC |
| https://github.com/pyca/pyopenssl/blob/358cbf29c4… | x_refsource_MISC |
Impacted products
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Browse all ATT&CK techniques and the vulnerabilities related to each.
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