# CVE-2026-40613: Coturn: Misaligned Memory Access in coturn STUN Attribute Parser (Remote DoS on ARM64)

> Remote unauthenticated attackers can crash ARM64 coturn servers via crafted UDP packets due to misaligned memory access in STUN parsing.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Apr 2026
- **Updated:** 21 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-40613, GHSA-j662-9wcj-mf36, MGASA-2026-0217, UBUNTU-CVE-2026-40613

## What is CVE-2026-40613?

CVE-2026-40613 is a high-severity denial of service vulnerability in coturn, published on 21 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-704 (Incorrect Type Conversion or Cast)

## Which versions are affected by CVE-2026-40613?

It affects 1 product.


Products: Coturn Project Coturn.

## How do I fix CVE-2026-40613?

Upgrade to a fixed version.

## Is CVE-2026-40613 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40613 exists.

## Other vulnerabilities in coturn

- [CVE-2018-4056](https://insights.sbomify.com/CVE-2018-4056/): SQL injection in coTURN (critical 9.1)
- [CVE-2026-43994](https://insights.sbomify.com/CVE-2026-43994/): Coturn: Stack buffer overflow in decode_oauth_token_gcm() (high 8.1)
- [CVE-2018-4058](https://insights.sbomify.com/CVE-2018-4058/): Server-side request forgery in coTURN (high 7.7)
- [CVE-2026-53450](https://insights.sbomify.com/CVE-2026-53450/): Coturn: IPv4-mapped 127.0.0.1 bypasses default loopback peer protection (high 7.4)
- [CVE-2026-53448](https://insights.sbomify.com/CVE-2026-53448/): Coturn: SQL Injection in HTTPS Admin Panel Delete Operations (high 7.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40613 and fix it if it is affected.

What it is: CVE-2026-40613 is a high-severity denial of service vulnerability in coturn, published on 21 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40613 exists.

Affected product: coturn. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-40613/ (Markdown: https://insights.sbomify.com/CVE-2026-40613/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40613
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40613
- OSV: https://osv.dev/vulnerability/CVE-2026-40613

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40613/
Summaries are generated and may contain mistakes; the official description above is the record.