A heap buffer overflow vulnerability exists in the DTLS handshake fragment reassembly logic of GnuTLS. The flaw occurs because the merge_handshake_packet() function merges fragments based only on handshake type without validating consistent message_length fields across fragments. This can lead to out-of-bounds heap writes when fragments with conflicting lengths are processed. The vulnerability is remotely exploitable without authentication and can cause application crashes or memory corruption.