cve 2026 27459

CVE-2026-27459 is a security vulnerability in pyOpenSSL involving a buffer overflow in the DTLS cookie callback. The flaw occurs when a DTLS cookie callback returns more bytes than the fixed-size OpenSSL buffer can hold, potentially corrupting adjacent memory. This issue was addressed in pyOpenSSL version 26.0.0. The vulnerability highlights how small boundary errors in glue code between a language runtime and a native crypto library can lead to serious security flaws. Users of pyOpenSSL should update to version 26.0.0 or later to mitigate the risk.