Zephyr Project up to 4.3.1 HTTP Client http_client.c print_header_field out-of-bounds

Summaryinfo

A vulnerability was found in Zephyr Project Zephyr up to 4.3.1. It has been rated as critical. This affects the function print_header_field of the file subsys/net/lib/http/http_client.c of the component HTTP Client. Performing a manipulation results in out-of-bounds. This vulnerability is cataloged as CVE-2026-90588. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Zephyr Project Zephyr up to 4.3.1. It has been classified as critical. This affects the function print_header_field of the file subsys/net/lib/http/http_client.c of the component HTTP Client. The manipulation with an unknown input leads to a out-of-bounds vulnerability. CWE is classifying the issue as CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. This is going to have an impact on availability. The summary by CVE is:

The HTTP client's debug helper print_header_field() in subsys/net/lib/http/http_client.c formatted an http_parser data-callback slice with a %s conversion: snprintk(output, len + 1, "%s", str). The parser hands its callbacks a pointer and a length into the caller's receive buffer, and those bytes are not NUL terminated. The size argument of snprintk() bounds only the destination, while the %s conversion measures the source first — lib/os/cbprintf_complete.c uses strlen() when no precision is given, and lib/os/cbprintf_nano.c uses strlen() unconditionally — so the read walks past the end of the header field and past the end of the receive buffer until it finds a zero byte. The slice reaches the helper from on_url(), on_header_field() and on_header_value(), which the parser invokes on bytes that http_wait_data() read straight off the socket into the application-supplied recv_buf. A malicious or compromised HTTP server, or an attacker able to answer a plaintext request, therefore controls both the header field and the bytes that follow it in the buffer, and can guarantee that no zero byte appears before the buffer ends, forcing the over-read. The in-tree tests/net/lib/http_client suite reproduces the over-read under CONFIG_ASAN=y on an ordinary GET. The impact is bounded. The whole helper body is compiled only when the HTTP client log module is explicitly set to Debug (CONFIG_NET_HTTP_LOG_LEVEL_DBG=y, which the global CONFIG_LOG_DEFAULT_LEVEL does not set), so default builds are unaffected. No out-of-bounds write occurs and none of the over-read bytes are emitted into the log, so there is no information disclosure; the consequence is an out-of-bounds read that can fault and panic the device where the buffer abuts an unmapped or MPU/MMU-protected region. The fix copies exactly the len bytes the parser offered with memcpy() and terminates them, instead of relying on a %s conversion (a %.*s precision would not have sufficed, since cbprintf_nano.c measures the source in full before applying it).

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-90588 since 09/12/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 4.3.2 or 4.5.0 eliminates this vulnerability. Applying the patch 0b2d0c2609cb0a4cd5cd82d2471e9ce8e3a14a8d is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Project Management Software

Vendor

• Zephyr Project

Name

• Zephyr

Version

• 4.3.0
• 4.3.1

CPE 2.3info

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CPE 2.2info

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