CVE-2026-40613

Coturn Project Coturn ≤ 4.10.0

Public PoC

Published

21 April 2026

Modified

24 April 2026

Patch / advisory

View advisory

CVSS Score v3.1 7.5

Click a component to see what it means

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Score 0.011 63th percentile

Risk Priority 60 floored blend · peak EPSS

Summary

CVE-2026-40613 is a high-severity Incorrect Type Conversion or Cast (CWE-704) vulnerability in Coturn Project Coturn. Its CVSS base score is 7.5 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 37% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-40613 is a vulnerability in Coturn, a free open source implementation of TURN and STUN servers, affecting versions prior to 4.10.0. The issue stems from unsafe pointer casts in the STUN/TURN attribute parsing functions within ns_turn_msg.c, where uint8_t pointers are cast to uint16_t pointers without alignment checks. Processing a crafted STUN message with odd-aligned attribute boundaries triggers misaligned memory reads, which on ARM64 (AArch64) architectures with strict alignment enforcement results in a SIGBUS signal that terminates the turnserver process.

An unauthenticated remote attacker can exploit this vulnerability by sending a single crafted UDP packet to any ARM64 Coturn deployment, causing an immediate denial-of-service crash of the turnserver process. The CVSS 3.1 score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) reflects its network accessibility, low complexity, and high availability impact with no privileges required.

The Coturn GitHub security advisory (GHSA-j662-9wcj-mf36) confirms the vulnerability and states it is fixed in version 4.10.0, recommending users upgrade to this release or later to mitigate the issue.

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2026-24228

Vulnerability Data

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.

CWE(s): CWE-704

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation

Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.

attack.mitre.org →

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1203 Exploitation for Client Execution Execution

Adversaries may exploit software vulnerabilities in client applications to execute code.

attack.mitre.org →

T1210 Exploitation of Remote Services Lateral Movement

Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.

attack.mitre.org →

T1212 Exploitation for Credential Access Credential Access

Adversaries may exploit software vulnerabilities in an attempt to collect credentials.

attack.mitre.org →

T1687 Exploitation for Defense Impairment Defense Impairment

Adversaries may exploit vulnerabilities in security software, infrastructure, or defensive components to degrade, disable, or otherwise continue to impair their ability to prevent, detect, or respond to malicious activity.

attack.mitre.org →

Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-43994Same product: Coturn Project Coturn

CVE-2026-53450Same product: Coturn Project Coturn

CVE-2026-53448Same product: Coturn Project Coturn

CVE-2026-53449Same product: Coturn Project Coturn

CVE-2026-43915Same product: Coturn Project Coturn

CVE-2026-27624Same product: Coturn Project Coturn

CVE-2025-37746Shared CWE-704

CVE-2024-39589Shared CWE-704

CVE-2023-21651Shared CWE-704

CVE-2025-12781Shared CWE-704

Affected Assets

coturn project

coturn

≤ 4.10.0

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation (static analysis, fuzzing, unit tests) directly finds incorrect type conversions or casts.

SA-15 Development Process, Standards, and Tools partial match

Requiring documented development standards and tools can mandate safe typing, casting rules, and compiler checks that stop the weakness from being introduced.

SA-8 Security and Privacy Engineering Principles partial match

Security engineering principles can require type-safe design and casting practices that structurally avoid incorrect conversions.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match

prevents

Secure SDLC practices directly prevent type-conversion flaws via coding standards, reviews, and testing.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match

finds

Security testing can uncover type-conversion defects before release.

A.8.25 Secure development life cycle partial match

prevents

Secure development lifecycle includes type-safety reviews that reduce incorrect casts.

A.8.26 Application security requirements partial match

prevents

Application security requirements can mandate strong typing and safe casting rules.

A.8.27 Secure system architecture and engineering principles partial match

degrades

Secure architecture principles discourage unsafe type conversions in design.