Copyright © 2012 Red Hat, Inc. All rights reserved. Important 2026-07-10T18:05:06 coturn: Coturn: Localhost services exposed via IPv4-mapped IPv6 address bypass 7.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L CWE-289

Coturn is a free open source implementation of TURN and STUN Server. Prior to 4.13.0, coturn rejects loopback peers by default unless allow-loopback-peers is enabled, but the default loopback guard can be bypassed by using the IPv4-mapped IPv6 peer address ::ffff:127.0.0.1 in a TURN XOR-PEER-ADDRESS attribute. ioa_addr_is_loopback checks for the literal IPv6 loopback shape before IPv4-mapped IPv6 handling, so good_peer_addr does not apply the default loopback rejection and an authenticated TURN client can expose services bound only to localhost on the coturn host through TURN relay traffic. This issue is fixed in version 4.13.0.

A flaw was found in Coturn, an open-source implementation of TURN and STUN servers. An authenticated TURN client can bypass the default loopback protection mechanism by using an IPv4-mapped IPv6 peer address. This allows the client to expose services that are intended to be accessible only from the local machine on the Coturn host through TURN relay traffic. This could lead to unauthorized access to internal services.

This flaw affects the community-maintained coturn TURN/STUN server as shipped in Fedora and EPEL. Red Hat does not ship coturn in any core Red Hat product. Fedora and EPEL currently ship coturn 4.14.0, which already includes the fix released in 4.13.0, so the shipped builds are not vulnerable to this loopback-protection bypass via IPv4-mapped IPv6 addresses. No action needed — the shipped coturn build (4.14.0) already contains the upstream fix. https://www.cve.org/CVERecord?id=CVE-2026-53450 https://nvd.nist.gov/vuln/detail/CVE-2026-53450 https://github.com/coturn/coturn/commit/b057acbebe721c8f2f202ddad5e16289e295c754 https://github.com/coturn/coturn/security/advisories/GHSA-w4hf-cr3w-6h79