CVE-2026-73215
Received Received - Intake

Coturn Server Port Exhaustion via Allocate Request

Publication date: 2026-08-11

Last updated on: 2026-08-11

Assigner: GitHub, Inc.

Description
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.

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Meta Information

Published
2026-08-11
Last Modified
2026-08-11
Generated
2026-08-11
AI Q&A
2026-08-11
EPSS Evaluated
N/A
NVD
CVE-2026-73215
EUVD
EUVD-2026-56823

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
coturn coturn 4.17.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-400 The product does not properly control the allocation and maintenance of a limited resource.
CWE-772 The product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed.

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Executive Summary

CVE-2026-73215 is a vulnerability in the Coturn TURN server where an improper handling of the EVEN-PORT attribute with the reservation bit (R) clear leads to port exhaustion. When a client requests an even relay port without reserving the next-higher odd port (R=0), the server incorrectly marks the odd sibling port as taken and never releases it. This causes a permanent loss of one port from the available pool per allocation, eventually exhausting the relay port range and causing allocation failures with error code 508.

Detection Guidance

To detect this vulnerability, monitor for repeated allocation failures with STUN error 508 in coturn logs. Check if the even-port option is enabled and if port exhaustion is occurring. Commands like 'ss -tulnp | grep turn' or 'netstat -tulnp | grep turn' can show active ports. Look for mismatches between allocated and available ports.

Impact Analysis

This vulnerability can cause the Coturn server to stop accepting new requests by exhausting the available relay ports. Attackers could repeatedly make TURN requests with the EVEN-PORT attribute to deplete the port pool, leading to denial of service. The server may appear to have no active allocations while rejecting new connections, resulting in service disruption for legitimate users.

Mitigation Strategies

Upgrade to coturn version 4.17.0 or later immediately. If upgrading is not possible, disable the even-port option in the coturn configuration file. Monitor port usage and allocation failures to identify potential exploitation attempts.

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