Critical [CVE-2026-73213] Server-Side Request Forgery via incorrect IPv6 comparison
This critical-severity Red Hat Linux advisory covers CVE-2026-73213.
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Summary
Coturn is a free open source implementation of TURN and STUN Server.
Prior to 4.16.0, addr_less_eq() in src/client/ns_turn_ioaddr.c uses a component-wise comparison for native IPv6 min-max intervals in ioa_addr_in_range(), allowing an authenticated TURN client to relay to an IPv6 peer that is numerically within a configured non-prefix-aligned denied-peer-ip range but is classified as outside it.
This issue is fixed in version 4.16.0. A flaw was found in Coturn.
An authenticated TURN client can bypass configured IP address restrictions due to an incorrect component-wise IPv6 comparison in the `addr_less_eq()` function. This allows the client to relay traffic to an IPv6 peer that should be denied, leading to a Server-Side Request Forgery (SSRF) vulnerability.
Red Hat products do not ship Coturn. The community packages (Fedora, EPEL) ship Coturn 4.16.0 which includes the fix for this vulnerability.
Red Hat severity: Critical — CVSS 9.9 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H). Weakness: CWE-918.
- < 4.16.0
Official advisory · high-confidence parse· fetched 3 hours ago·verify at source
Mitigation checklist
- Update Coturn to version 4.16.0 or later, which replaces the incorrect component-wise IPv6 comparison with a correct memcmp-based ordering.
Official advisory · high-confidence parse· fetched 3 hours ago·verify at source
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