Buffer overflow in Zephyrproject Zephyr
CVE-2026-5067
A remote, unauthenticated attacker can trigger memory corruption in Zephyr's HTTP server WebSocket upgrade path by sending a crafted Sec-WebSocket-Key header. The HTTP/1 header parser copies the header into a fixed-size buffer using a bounded copy that does not guarantee NUL termination when the input length reaches the buffer size. During upgrade handling the buffer is copied to a local stack buffer and passed to strlen(); if no NUL exists in-bounds, strlen() reads beyond the stack buffer and subsequent concatenation with the WebSocket magic string can write out of bounds. This leads to out-of-bounds read and write on stack memory, resulting in crash (denial of service) and potentially code execution. The path is reachable when CONFIG_HTTP_SERVER_WEBSOCKET is enabled.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.006 (50.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 50.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.009 · newest: 0.006 · change: -0.002
Affected products
- Zephyrproject Zephyr
- Zephyrproject-Rtos Zephyr — versions 3.7.0
Weakness classification (CWE)
References
- github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-wgr4-9pwq-94vj (Exploit, Patch, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-5067?
- CVE-2026-5067 is a critical-severity vulnerability in Zephyrproject Zephyr, classified under Improper Null Termination. CVSS score: 9.8/10. Published 2026-06-09.
- How severe is CVE-2026-5067?
- Critical severity. CVSS v3 base score is 9.8 out of 10.