Ubuntu Security Notices USN-8335-1 USN-8335-1: pyOpenSSL vulnerability Publication date 28 May 2026 Overview pyOpenSSL could allow unintended access to network services. Releases 20.04 LTS 18.04 LTS 16.04 LTS Open side navigation Close side navigation Packages Details Update instructions References Related notices Packages pyopenssl - Python wrapper around the OpenSSL library Details It was discovered that pyOpenSSL incorrectly handled exceptions in the tlsext_servername callback. This could result in connections being accepted after an exception, contrary to expectations. It was discovered that pyOpenSSL incorrectly handled exceptions in the tlsext_servername callback. This could result in connections being accepted after an exception, contrary to expectations. Update instructions In general, a standard system update will make all the necessary changes. Learn more about how to get the fixes. The problem can be corrected by updating your system to the following package versions: Ubuntu Release Package Version 20.04 LTS focal python-openssl – 19.0.0-1ubuntu0.1~esm1 Ubuntu Pro Fix available with Ubuntu Pro . python3-openssl – 19.0.0-1ubuntu0.1~esm1 Ubuntu Pro Fix available with Ubuntu Pro . 18.04 LTS bionic python-openssl – 17.5.0-1ubuntu1+esm1 Ubuntu Pro Fix available with Ubuntu Pro . python3-openssl – 17.5.0-1ubuntu1+esm1 Ubuntu Pro Fix available with Ubuntu Pro . 16.04 LTS xenial python-openssl – 0.15.1-2ubuntu0.2+esm1 Ubuntu Pro Fix available with Ubuntu Pro via Legacy Support add-on. python3-openssl – 0.15.1-2ubuntu0.2+esm1 Ubuntu Pro Fix available with Ubuntu Pro via Legacy Support add-on. Reduce your security exposure Ubuntu Pro provides ten-year security coverage to 25,000+ packages in Main and Universe repositories, and it is free for up to five machines. Get Ubuntu Pro References CVE-2026-27448 CVE-2026-27448 Related notices USN-8115-1 USN-8115-1