CVE-2026-27448
pyOpenSSL allows TLS connection bypass via unhandled callback exception in set_tlsext_servername_callback
- State
- Published
- Severity
- 1.7 Low
- Published
- Mar 17, 2026
- Updated
- Mar 18, 2026
- Reserved
- Feb 19, 2026
Description
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 | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 1.7 Low | 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 | GitHub_M |
Weaknesses
- CWE-636 Not Failing Securely ('Failing Open')
Affected Products
| Product | Versions |
|---|---|
pyopensslpyca |
|
References
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