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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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.
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.
Sources
Also known as DEBIAN-CVE-2026-62959, GHSA-m23x-5qf5-988g, UBUNTU-CVE-2026-62959.