CVE-2026-53450 Coturn: IPv4-mapped 127.0.0.1 bypasses default loopback peer protection
An authenticated attacker can bypass loopback protection to access localhost services via IPv4-mapped IPv6 addresses in TURN relay traffic.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53450?
CVE-2026-53450 is a high-severity server-side request forgery vulnerability in coturn, published on 10 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Weakness: CWE-918
Which versions are affected by CVE-2026-53450?
It affects 1 product.
Products include Coturn Project Coturn.
How do I fix CVE-2026-53450?
Upgrade to a fixed version.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-53450 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53450 exists.
Other vulnerabilities in coturn
- CVE-2018-4056 SQL injection in coTURN
- CVE-2026-43994 Coturn: Stack buffer overflow in decode_oauth_token_gcm()
- CVE-2018-4058 Server-side request forgery in coTURN
- CVE-2026-40613 Coturn: Misaligned Memory Access in coturn STUN Attribute Parser (Remote DoS on ARM64)
- CVE-2026-53448 Coturn: SQL Injection in HTTPS Admin Panel Delete Operations
Sources
Also known as DEBIAN-CVE-2026-53450, GHSA-w4hf-cr3w-6h79, UBUNTU-CVE-2026-53450.