CVE-2026-27459 — pyOpenSSL DTLS cookie callback buffer overflow

Affected: pyca pyopenssl, Red Hat Ansible Automation Platform 2.5 for RHEL 8, Red Hat Ansible Automation Platform 2.5 for RHEL 9, Red Hat Ansible Automation Platform 2.6 for RHEL 9, Red Hat Satellite 6.16 for RHEL 8, Red Hat Satellite 6.16 for RHEL 9, Red Hat Satellite 6.17 for RHEL 9, Red Hat Satellite 6.18 for RHEL 9, Red Hat RHUI 4 for RHEL 8, Red Hat Ansible Automation Platform 2.5 and 30 more

pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 22.0.0 and prior to version 26.0.0, if a user provided callback to `set_cookie_generate_callback` returned a cookie value greater than 256 bytes, pyOpenSSL would overflow an OpenSSL provided buffer. Starting in version 26.0.0, cookie values that are too long are now rejected.

USN-8115-1 — pyopenssl vulnerabilities

Affected: Ubuntu:22.04:LTS: pyopenssl, Ubuntu:24.04:LTS: pyopenssl, Ubuntu:25.10: pyopenssl

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. (CVE-2026-27448)

It was discovered that pyOpenSSL incorrectly handled the DTLS cookie generation callback. If a callback provided cookie values greater than 256 bytes, an attacker could use this issue to cause pyOpenSSL to crash, resulting in a denial of service, or possibly execute arbitrary code. This issue only affected Ubuntu 24.04 LTS and Ubuntu 25.10. (CVE-2026-27459)

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CVE-2026-27459 — pyOpenSSL DTLS cookie callback buffer overflow

USN-8115-1 — pyopenssl vulnerabilities