What is CVE-2026-40613?

CVE-2026-40613 is a high-severity vulnerability in Coturn, classified under Incorrect Type Conversion or Cast. CVSS score: 7.5/10. Published 2026-04-21.

How severe is CVE-2026-40613?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Coturn

CVE-2026-40613

Coturn is a free open source implementation of TURN and STUN Server. Prior to 4.10.0, the STUN/TURN attribute parsing functions in coturn perform unsafe pointer casts from uint8_t * to uint16_t * without alignment checks. When processing a crafted STUN message with odd-aligned attribute boundaries, this results in misaligned memory reads at ns_turn_msg.c. On ARM64 architectures (AArch64) with strict alignment enforcement, this causes a SIGBUS signal that immediately kills the turnserver process. An unauthenticated remote attacker can crash any ARM64 coturn deployment by sending a single crafted UDP packet. This vulnerability is fixed in 4.10.0.

Published 2026-04-21 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.015 (73.6th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 74th percentile — 73.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.011 · newest: 0.015 · change: +0.004

Affected products

Coturn — versions < 4.10.0
Coturn Project

Weakness classification (CWE)

CWE-704 — Incorrect Type Conversion or Cast

References

github.com/coturn/coturn/security/advisories/GHSA-j662-9wcj-mf36 (Exploit, Vendor Advisory)

Frequently asked questions

What is CVE-2026-40613?: CVE-2026-40613 is a high-severity vulnerability in Coturn, classified under Incorrect Type Conversion or Cast. CVSS score: 7.5/10. Published 2026-04-21.
How severe is CVE-2026-40613?: High severity. CVSS v3 base score is 7.5 out of 10.