p PatchFirst

CVE-2026-27448

CVE-2026-27448 · pyOpenSSL allows TLS connection bypass via unhandled callback exception in set_tlsext_servername_callback

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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 1.7 · Low · EPSS 0.3% · Fix available

Published
Updated

Stack: system · python

Affected products and versions

  • pyopenssl

    Versions
    • >= 0.14.0, < 26.0.0: Affected

    No fix published

  • pyopenssl Debian:12

    Versions
    • 23.0.0-1
    • 23.2.0-1
    • 24.0.0-1
    • 24.0.0-2
    • 24.0.0-3
    • 24.0.0-4
    • 24.0.0-5
    • 24.1.0-1
    • 24.2.1-1
    • 24.3.0-1
    • 25.0.0-1
    • 25.1.0-1
    • 25.1.0-2
    • 25.3.0-1
    • 25.3.0-2
    • 26.0.0-1
    • 26.1.0-1
    • 26.2.0-1
    • 26.2.0-1~exp1
    • 26.3.0-1
    • 26.3.0-1~exp1
    • 26.4.0-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • pyopenssl Debian:13

    Versions
    • 25.0.0-1
    Affected ranges
    • ECOSYSTEM: < 25.0.0-1+deb13u1

    Update to 25.0.0-1+deb13u1

  • pyopenssl Debian:14

    Versions
    • 25.0.0-1
    • 25.1.0-1
    • 25.1.0-2
    • 25.3.0-1
    • 25.3.0-2
    Affected ranges
    • ECOSYSTEM: < 26.0.0-1

    Update to 26.0.0-1

  • pyopenssl PyPI

    Versions
    • 0.14
    • 0.15
    • 0.15.1
    • 16.0.0
    • 16.1.0
    • 16.2.0
    • 17.0.0
    • 17.1.0
    • 17.2.0
    • 17.3.0
    • 17.4.0
    • 17.5.0
    • 18.0.0
    • 19.0.0
    • 19.1.0
    • 20.0.0
    • 20.0.1
    • 21.0.0
    • 22.0.0
    • 22.1.0
    • 23.0.0
    • 23.1.0
    • 23.1.1
    • 23.2.0
    • 23.3.0
    • 24.0.0
    • 24.1.0
    • 24.2.1
    • 24.3.0
    • 25.0.0
    • 25.1.0
    • 25.2.0
    • 25.3.0
    Affected ranges
    • ECOSYSTEM: ≥ 0.14.0, < 26.0.0

    Update to 26.0.0

  • pyopenssl PyPI

    Versions
    • 0.14
    • 0.15
    • 0.15.1
    • 16.0.0
    • 16.1.0
    • 16.2.0
    • 17.0.0
    • 17.1.0
    • 17.2.0
    • 17.3.0
    • 17.4.0
    • 17.5.0
    • 18.0.0
    • 19.0.0
    • 19.1.0
    • 20.0.0
    • 20.0.1
    • 21.0.0
    • 22.0.0
    • 22.1.0
    • 23.0.0
    • 23.1.0
    • 23.1.1
    • 23.2.0
    • 23.3.0
    • 24.0.0
    • 24.1.0
    • 24.2.1
    • 24.3.0
    • 25.0.0
    • 25.1.0
    • 25.2.0
    • 25.3.0
    Affected ranges
    • ECOSYSTEM: ≥ 0.14, < 26.0.0

    Update to 26.0.0

  • pyopenssl Ubuntu:Pro:16.04:LTS

    Versions
    • 0.15.1-2build1
    • 0.15.1-2ubuntu0.2
    Affected ranges
    • ECOSYSTEM: < 0.15.1-2ubuntu0.2+esm1

    Update to 0.15.1-2ubuntu0.2+esm1

  • pyopenssl Ubuntu:Pro:18.04:LTS

    Versions
    • 16.2.0-1
    • 17.5.0-1
    • 17.5.0-1ubuntu1
    Affected ranges
    • ECOSYSTEM: < 17.5.0-1ubuntu1+esm1

    Update to 17.5.0-1ubuntu1+esm1

  • pyopenssl Ubuntu:Pro:20.04:LTS

    Versions
    • 19.0.0-1
    • 19.0.0-1build1
    Affected ranges
    • ECOSYSTEM: < 19.0.0-1ubuntu0.1~esm1

    Update to 19.0.0-1ubuntu0.1~esm1

  • pyopenssl Ubuntu:22.04:LTS

    Versions
    • 20.0.1-1
    • 21.0.0-1
    Affected ranges
    • ECOSYSTEM: < 21.0.0-1ubuntu0.1

    Update to 21.0.0-1ubuntu0.1

  • pyopenssl Ubuntu:24.04:LTS

    Versions
    • 23.0.0-1
    • 23.2.0-1
    Affected ranges
    • ECOSYSTEM: < 23.2.0-1ubuntu0.1

    Update to 23.2.0-1ubuntu0.1

  • pyopenssl Ubuntu:25.10

    Versions
    • 25.0.0-1
    Affected ranges
    • ECOSYSTEM: < 25.0.0-1ubuntu0.1

    Update to 25.0.0-1ubuntu0.1

Original sources

Check your server →