pyOpenSSL allows TLS connection bypass via unhandled callback exception in set_tlsext_servername_callback
CVE-2026-27448 is fixed in 7 products on 1 platform, first by python-openssl 17.5.0-1ubuntu1+esm1, released March 17, 2026. It is not reported as exploited. Patch Radar priority: Routine.
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.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| pyopenssl · Debian 13.5 (trixie) | 25.0.0-1+deb13u1 | DEBIAN-CVE-2026-27448 | Mar 18, 2026 |
| pyopenssl · Debian 14 | 26.0.0-1 | DEBIAN-CVE-2026-27448 | Mar 18, 2026 |
| python-openssl · Ubuntu 18.04.6 LTS (bionic) | 17.5.0-1ubuntu1+esm1 | python-openssl 17.5.0-1ubuntu1+esm1 | Mar 17, 2026 |
| python-openssl · Ubuntu 20.04 LTS (focal) | 19.0.0-1ubuntu0.1~esm1 | python-openssl 19.0.0-1ubuntu0.1~esm1 | Mar 17, 2026 |
| python-pyOpenSSL · opensuse-leap 15.6 | 23.2.0-150400.3.13.1 | SUSE-SU-2026:1192-1 | Apr 7, 2026 |
| python-pyOpenSSL · opensuse-leap 16.0 | 25.0.0-160000.3.1 | OPENSUSE-SU-2026:20419-1 | Mar 25, 2026 |
| python-pyOpenSSL · sles 15.6 | 23.2.0-150400.3.13.1 | SUSE-SU-2026:1192-1 | Apr 7, 2026 |
| python-pyOpenSSL · sles 15.7 | 23.2.0-150400.3.13.1 | SUSE-SU-2026:1192-1 | Apr 7, 2026 |
| python-pyOpenSSL · sles 16.0 | 25.0.0-160000.3.1 | SUSE-SU-2026:20930-1 | Mar 25, 2026 |
| python3-openssl · Ubuntu 18.04.6 LTS (bionic) | 17.5.0-1ubuntu1+esm1 | python3-openssl 17.5.0-1ubuntu1+esm1 | Mar 17, 2026 |
| python3-openssl · Ubuntu 20.04 LTS (focal) | 19.0.0-1ubuntu0.1~esm1 | python3-openssl 19.0.0-1ubuntu0.1~esm1 | Mar 17, 2026 |
| python3-openssl · Ubuntu 22.04.1 LTS (jammy) | 21.0.0-1ubuntu0.1 | python3-openssl 21.0.0-1ubuntu0.1 | Apr 15, 2026 |
| python3-openssl · Ubuntu 24.04.5 LTS (noble) | 23.2.0-1ubuntu0.1 | python3-openssl 23.2.0-1ubuntu0.1 | Apr 15, 2026 |
| python3-openssl · Ubuntu 25.10 (questing) | 25.0.0-1ubuntu0.1 | python3-openssl 25.0.0-1ubuntu0.1 | Apr 15, 2026 |
| python3-pyOpenSSL · ol 9 | 0:19.0.0-1.0.3.el9 | ELSA-2026-50324 | Jun 24, 2026 |
| python3-pyOpenSSL · sles 15.7 | 21.0.0-150400.22.1 | SUSE-SU-2026:3424-1 | Jul 30, 2026 |
| python39-oci-sdk · ol 9 | 0:2.187.0-1.0.5.el9 | ELSA-2026-604898 | Nov 7, 2026 |
| python39-oci-sdk-docs · ol 9 | 0:2.187.0-1.0.5.el9 | ELSA-2026-604898 | Nov 7, 2026 |
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