zephyrproject-rtos Zephyr up to 4.3.0 WebSocket Upgrade strlen null termination

Summaryinfo

A vulnerability identified as very critical has been detected in zephyrproject-rtos Zephyr up to 4.3.0. This impacts the function strlen of the component WebSocket Upgrade Handler. The manipulation leads to null termination. This vulnerability is referenced as CVE-2026-5067. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in zephyrproject-rtos Zephyr up to 4.3.0 and classified as very critical. This issue affects the function strlen of the component WebSocket Upgrade Handler. The manipulation with an unknown input leads to a null termination vulnerability. Using CWE to declare the problem leads to CWE-170. The product does not terminate or incorrectly terminates a string or array with a null character or equivalent terminator. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-5067 since 03/27/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/09/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• Project Management Software

Vendor

• zephyrproject-rtos

Name

• Zephyr

Version

• 4.0
• 4.1
• 4.2
• 4.3.0

License

• open-source

Website

• Product: https://github.com/zephyrproject-rtos/zephyr/

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