# CVE-2026-62959: Coturn: Pre-authentication heap memory disclosure in ACME redirect (`try_acme_redirect`)

> Unauthenticated attackers can leak heap memory containing sensitive data via a crafted HTTP request when ACME redirect is enabled.

- **Severity:** High 8.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 31 Jul 2026
- **Updated:** 31 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-62959, GHSA-m23x-5qf5-988g, UBUNTU-CVE-2026-62959

## What is CVE-2026-62959?

CVE-2026-62959 is a high-severity vulnerability in coturn, published on 31 Jul 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. From 4.5.2 through 4.14.0, when Coturn is started with --acme-redirect <URL> and exposes a plaintext-TCP listener, an unauthenticated remote client can send a single ordinary HTTP GET request and receive a 301 response whose Location header contains up to ~870 bytes of adjacent process heap memory. The leaked region is a recycled network receive buffer that is reused without being zeroed, so on a busy server it can contain data from other clients' requests (TURN credentials, OAuth tokens, relayed payloads). Root cause is a signed→unsigned conversion. This issue is fixed in version 4.15.0.

Weakness: CWE-195 (Signed to Unsigned Conversion Error), CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-62959?


## How do I fix CVE-2026-62959?

Upgrade to a fixed version.

## Is CVE-2026-62959 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-62959 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-62959 and fix it if it is affected.

What it is: CVE-2026-62959 is a high-severity vulnerability in coturn, published on 31 Jul 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-2026-62959 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-2026-62959/ (Markdown: https://insights.sbomify.com/CVE-2026-62959/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-62959
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-62959
- OSV: https://osv.dev/vulnerability/CVE-2026-62959

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-62959/
Summaries are generated and may contain mistakes; the official description above is the record.