CVE-2026-53450: Coturn: IPv4-mapped 127.0.0.1 bypasses default loopback peer protection
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. ioaaddrisloopback checks for the literal IPv6 loopback shape before IPv4-mapped IPv6 handling, so goodpeeraddr 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.
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2026-53450?
The severity of CVE-2026-53450 is high, with a CVSS score of 7.4.
How do I fix CVE-2026-53450?
To fix CVE-2026-53450, upgrade to Coturn version 4.13.0 or later to ensure that the loopback peer protection is enforced.
What are the potential impacts of CVE-2026-53450?
CVE-2026-53450 allows unauthorized access to the server through IPv4-mapped IPv6 addresses, compromising the confidentiality and integrity of communications.
What software is affected by CVE-2026-53450?
CVE-2026-53450 specifically affects Coturn versions prior to 4.13.0.
What type of vulnerability is CVE-2026-53450 classified as?
CVE-2026-53450 is classified as a Server-Side Request Forgery (SSRF) vulnerability.