Quick answers
- Is CVE-2026-5067 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-5067 being exploited in the wild.
- How severe is CVE-2026-5067?
- Critical severity, with a CVSS score of 9.8, published 9 June 2026.
- Which products and versions are affected?
- Zephyr Project Zephyr >= 3.7.0, <= 4.3.0.
- Is there a fix for CVE-2026-5067?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-5067 attacked?
- It is attacked over the network, in an operating system.
- Am I affected by CVE-2026-5067?
- Check whether you run Zephyr Project Zephyr at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
A stack-based out-of-bounds read and write vulnerability exists in Zephyr's HTTP/1.1 server during WebSocket upgrade handling. The root cause is an improper null termination (CWE-170) in the header parser; when a 32-byte 'Sec-WebSocket-Key' is received, it is copied into a fixed-size buffer without a guaranteed NUL terminator. Subsequent processing in 'http_server_ws.c' copies this data to a local stack buffer and calls 'strlen()', which reads past the buffer bounds. This leads to an out-of-bounds write when the server attempts to concatenate the WebSocket magic string. An unauthenticated remote attacker can exploit this to cause a denial of service (crash) or achieve remote code execution. The vulnerability is reachable only when CONFIG_HTTP_SERVER_WEBSOCKET is enabled.
Affected products
- Zephyr Project Zephyr RTOS >= 3.7.0, <= 4.3.0
Timeline
- 2026-05-23: other: Embargo date
- 2026-06-09: disclosed: Initial publication date
- 2026-06-09: advisory