CVE-2026-68553
HighCVSS 7.1Summary
In Coturn before 4.13.0, an authenticated TURN user can place printf-style format specifiers in STUN USERNAME or REALM attributes, which pass is_secure_string() validation and are embedded into Redis keys. send_message_to_redis() passes the attacker-controlled key as the format argument to redisAsyncCommand(), causing reads past the va_list. Exploitation can crash the coturn process or disclose stack memory into Redis.
Risk Assessment
The risk includes denial of service for TURN sessions and potential disclosure of sensitive stack memory to Redis, compromising confidentiality.
Recommendation
Upgrade Coturn to version 4.13.0 or later immediately. Also restrict access to authenticated TURN accounts and monitor logs for unusual patterns.
Original NVD description (English source)
Coturn is a free open source implementation of TURN and STUN Server. Prior to 4.13.0, an authenticated TURN user can place printf-style format specifiers in the STUN USERNAME or REALM attribute, which passes is_secure_string() validation and is embedded into Redis keys at nine call sites in src/apps/relay/ns_ioalib_engine_impl.c. send_message_to_redis() in src/apps/relay/hiredis_libevent2.c then passes the attacker-controlled key as the format argument to redisAsyncCommand() while supplying only one variadic value, causing hiredis redisvFormatCommand() to read past the va_list. Exploitation can crash the coturn process and terminate active TURN sessions or disclose stack memory into Redis. This issue is fixed in version 4.13.0.