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Vulnerability · Published Aug 19, 2026 · Assigned by GitHub_M

CVE-2026-68553Coturn: Format String Injection via TURN USERNAME/REALM into hiredis Redis Command

High 7.1

In plain English

A high-severity security flaw in coturn from coturn. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.1High
Exploit odds (30 days)0.5%top 58.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12coturnno fix listedDEBIAN-CVE-2026-68553
Debian:13coturnno fix listedDEBIAN-CVE-2026-68553
Debian:14coturn4.14.0-1DEBIAN-CVE-2026-68553
Ubuntu:22.04:LTScoturnno fix listedUBUNTU-CVE-2026-68553
Ubuntu:24.04:LTScoturnno fix listedUBUNTU-CVE-2026-68553
Ubuntu:26.04:LTScoturnno fix listedUBUNTU-CVE-2026-68553
Ubuntu:26.10coturnno fix listedUBUNTU-CVE-2026-68553

Affected products (as reported)

VendorProductVersions
coturn coturn < 4.13.0

Weakness: CWE-134 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H

References