---
id: CVE-2026-68553
title: Coturn is a free open source implementation of TURN and STUN Server
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…
severity: high
cvss: 7.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H'
cwe:
  - CWE-134
vendor: coturn
product: coturn
affected:
  - coturn < 4.13.0
published: '2026-08-19'
updated: '2026-09-09'
sourceUpdated: '2026-09-09T21:20:38.860'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-68553'
references:
  - url: >-
      https://github.com/coturn/coturn/commit/8fa38032bb4751e11e072d65a8eca3c06c950979
    label: security-advisories@github.com
  - url: 'https://github.com/coturn/coturn/releases/tag/4.13.0'
    label: security-advisories@github.com
  - url: 'https://github.com/coturn/coturn/security/advisories/GHSA-4g7c-p5wg-j4hp'
    label: security-advisories@github.com
  - url: 'https://github.com/coturn/coturn/security/advisories/GHSA-4g7c-p5wg-j4hp'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - cve.org
  - exploit-available
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-08-20T19:48:40.817549Z'
ingestedAt: '2026-09-13T21:18:26.997Z'
epss: 0.0048
epssPercentile: 0.38912
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.