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Vulnerability record · CVE-2026-68553 · published 19 August 2026

CVE-2026-68553: Coturn is a free open source implementation of TURN and STUN Server.

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.

7.1 CVSS 3.1 High EPSS 0.48% · top 61.1% CWE-134 · CWE-134 Deferred
7.1CVSS 3.1 base score
0.48%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
4References
9 Sep 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H

References

LinkTags
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

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Source: NIST National Vulnerability Database (record CVE-2026-68553), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.