CVE-2026-5067: zephyrproject-rtos Zephyr · Improper Null Termination
Affects zephyrproject-rtos ZephyrSource CVE Database V5
Not known to be exploited · CVSS 9.8 Critical : upgrade to 4.3.1 as a priority.
Data as of 30 Oct 2026, 11:52 UTC
- EPSS
- 0.6% chance of exploitation in 30 days – higher than 50% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 4.3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 9 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Upgrade zephyrproject-rtos Zephyr to 4.3.1.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| zephyrproject-rtosZephyr | Affected
| Fixed in
|
GitHubzephyrproject-rtos/zephyrpkg:github/zephyrproject-rtos/zephyrOther threats | Affected
| Fixed in– |
GitHubZephyrpkg:github/ZephyrOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
If you cannot patch yet, consider disabling the HTTP server WebSocket feature (CONFIG_HTTP_SERVER_WEBSOCKET) if feasible to mitigate exposure.
Description
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.