CVE-2026-53450
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.
What this means
- Exposure
- Exploitable remotely over the network, with an ordinary user account and with no action from the victim.
- Impact
- An attacker can read some data, alter some data and degrade the service. The impact spreads beyond the vulnerable component into other parts of the system.
- Weakness
- The server issues a request to an attacker-chosen address, reaching into the internal network (SSRF).
- Likelihood
- Its EPSS score stays low: nothing points to imminent exploitation, which is no reason to leave it unpatched.
What to doFold into the next patch cycle.
Read automatically from the CVSS vector, the weakness type (CWE) and the EPSS score. The technical description above remains the one published by NIST.