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VulnerabilityPublished Updated

CVE-2026-5067: zephyrproject-rtos Zephyr · Improper Null Termination

Affects zephyrproject-rtos ZephyrSource CVE Database V5

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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

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
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:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 9 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

ProductAffectedFixed in
zephyrproject-rtosZephyrAffected
  • >=3.7.0 <4.3.1
Fixed in
  • 4.3.1
GitHubzephyrproject-rtos/zephyrpkg:github/zephyrproject-rtos/zephyrOther threatsAffected
  • =3.7.0
Fixed in–
GitHubZephyrpkg:github/ZephyrOther threatsAffected
  • >=3.7.0 <4.3.1
Fixed in
  • 4.3.1

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.

References

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