CVE-2026-68553 Coturn: Format String Injection via TURN USERNAME/REALM into hiredis Redis Command
An authenticated user can inject format specifiers into TURN attributes, causing crashes or memory disclosure via Redis command formatting.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-68553?
CVE-2026-68553 is a high-severity vulnerability in coturn, published on 19 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Weakness: CWE-134
Which versions are affected by CVE-2026-68553?
How do I fix CVE-2026-68553?
Upgrade to a fixed version.
Is CVE-2026-68553 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-68553 exists.
Sources
Also known as DEBIAN-CVE-2026-68553, GHSA-4g7c-p5wg-j4hp, UBUNTU-CVE-2026-68553.