Eclipse tinydtls before commit b3efd41ad111a4920f599f51ffa4f5e9f1e72221 contains an out-of-bounds read vulnerability in the check_server_certificate() function that allows unauthenticated attackers to trigger reads beyond valid buffer boundaries by crafting a Certificate handshake message with a specific fragment_length value. Attackers can exploit missing buffer length validation before uint24 reads, memcmp, and memcpy operations during DTLS epoch 0 on both client and server paths to cause denial of service on memory-constrained devices.