CVE-2026-68553

Summary

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.

Affected Software

Weaknesses

• CWE-134: CWE-134: Use of Externally-Controlled Format String

References

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

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