Medium [CVE-2026-73215] Denial of Service due to incorrect port allocation
This medium-severity Red Hat Linux advisory covers CVE-2026-73215.
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Summary
Coturn is a free open source implementation of TURN and STUN Server.
Prior to 4.17.0, turnports_allocate_even() in src/apps/relay/turn_ports.c marks the unused odd sibling port as TPS_TAKEN_ODD for an EVEN-PORT Allocate request with reservation bit R=0 even though no RTCP socket will release it, allowing an authenticated client to permanently exhaust the relay port pool and cause subsequent allocations to fail with STUN error 508.
This issue is fixed in version 4.17.0. A flaw was found in Coturn.
An authenticated client can exploit a vulnerability by sending a specially crafted 'EVEN-PORT Allocate request' with a reservation bit set to zero. This causes the server to incorrectly mark an unused port as taken, leading to the permanent exhaustion of the relay port pool.
Consequently, new connection allocations will fail, resulting in a Denial of Service (DoS) for legitimate users. This Moderate impact 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. By sending a crafted port allocation request, an attacker can permanently exhaust the server's relay port pool, preventing new connections.
Red Hat severity: Moderate — CVSS 6.5 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-772.
- < 4.17.0
Official advisory · high-confidence parse· fetched 3 hours ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. Upgrade to coturn 4.17.0.
Official advisory · high-confidence parse· fetched 3 hours ago·verify at source
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