CVE-2026-68553

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.

• CWE-134

• https://github.com/coturn/coturn/commit/8fa38032bb4751e11e072d65a8eca3c06c950979
• https://github.com/coturn/coturn/releases/tag/4.13.0
• https://github.com/coturn/coturn/security/advisories/GHSA-4g7c-p5wg-j4hp
• https://github.com/coturn/coturn/security/advisories/GHSA-4g7c-p5wg-j4hp

Published

Aug 19, 2026

Last Modified

Sep 9, 2026

Status

Deferred

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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