CVE-2025-65499: Libcoap

Medium severity, CVSS 4.3. EPSS: 0.3% chance of exploitation in the next 30 days.

Array index error in tls_verify_call_back() in src/coap_openssl.c in OISM libcoap 4.3.5 allows remote attackers to cause a denial of service via a crafted DTLS handshake that triggers SSL_get_ex_data_X509_STORE_CTX_idx() to return -1.

Affected products

• Libcoap Libcoap: version 4.3.5 only

Published 2025-11-24. Last modified 2026-06-17.