OESA-2026-2331

GnuTLS is a secure communications library implementing the SSL, TLS and DTLS protocols and technologies around them. It provides a simple C language application programming interface (API) to access the secure communications protocols as well as APIs to parse and write X.509, PKCS #12, and other required structures. The project strives to provide a secure communications back-end, simple to use and integrated with the rest of the base Linux libraries. A back-end designed to work and be secure out of the box, keeping the complexity of TLS and PKI out of application code.

Security Fix(es):

A heap buffer overflow vulnerability exists in the DTLS handshake fragment reassembly logic of GnuTLS. The issue arises in mergehandshakepacket() where incoming handshake fragments are matched and merged based solely on handshake type, without validating that the messagelength field remains consistent across all fragments of the same logical message. An attacker can exploit this by sending crafted DTLS fragments with conflicting messagelength values, causing the implementation to allocate a buffer based on a smaller initial fragment and subsequently write beyond its bounds using larger, inconsistent fragments. Because the merge operation does not enforce proper bounds checking against the allocated buffer size, this results in an out-of-bounds write on the heap. The vulnerability is remotely exploitable without authentication via the DTLS handshake path and can lead to application crashes or potential memory corruption.(CVE-2026-33846)