ZephyrProject Zephyr up to 4.4.1 Flash Driver API flash_util.c z_vrfy_flash_copy src_dev/dst_dev sandbox

Summaryinfo

A vulnerability categorized as very critical has been discovered in ZephyrProject Zephyr up to 4.4.1. This affects the function z_vrfy_flash_copy of the file drivers/flash/flash_util.c of the component Flash Driver API. Such manipulation of the argument src_dev/dst_dev leads to sandbox. This vulnerability is uniquely identified as CVE-2026-9771. Local access is required to approach this attack. No exploit exists.

Detailsinfo

A vulnerability, which was classified as very critical, has been found in ZephyrProject Zephyr up to 4.4.1. Affected by this issue is the function z_vrfy_flash_copy of the file drivers/flash/flash_util.c of the component Flash Driver API. The manipulation of the argument src_dev/dst_dev with an unknown input leads to a sandbox vulnerability. Using CWE to declare the problem leads to CWE-265. Impacted is confidentiality, integrity, and availability. CVE summarizes:

The flash_copy() system call is verified by z_vrfy_flash_copy() in drivers/flash/flash_util.c. On builds with CONFIG_USERSPACE enabled, this handler is the kernel-side trust boundary for a user-mode caller. Prior to the fix it validated only the output buffer (K_SYSCALL_MEMORY_WRITE) and passed the two struct device * arguments, src_dev and dst_dev, directly into the implementation without any object validation — unlike every sibling flash syscall, which guards its device pointer with K_SYSCALL_DRIVER_FLASH. A user-mode thread fully controls the values of src_dev/dst_dev and the contents of its own address space. The implementation z_impl_flash_copy() dereferences these pointers and calls through their driver-API function tables (e.g. api->get_parameters(dst_dev), flash_read(src_dev, ...), flash_write(dst_dev, ...)). By supplying a pointer to a forged struct device whose api table contains attacker-chosen function pointers, an unprivileged thread can cause the kernel to call arbitrary code in supervisor mode; passing any arbitrary or invalid address otherwise yields a kernel crash or out-of-bounds read. The result is a local privilege escalation out of the userspace sandbox (with kernel denial-of-service and information disclosure as lesser outcomes). The fix adds K_SYSCALL_DRIVER_FLASH(src_dev, read) and K_SYSCALL_DRIVER_FLASH(dst_dev, write) to z_vrfy_flash_copy(), which verify each device is a registered flash-driver kernel object the calling thread is permitted to use before any dereference, closing the path completely.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-9771 since 05/28/2026. The exploitation is known to be easy. Local access is required to approach this attack. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 08/17/2026). This vulnerability is assigned to T1611 by the MITRE ATT&CK project.

Upgrading to version 4.4.2 eliminates this vulnerability. Applying the patch 1b1ecdc438092cdd469319a0d51cba6cf82e06f4 is able to eliminate this problem.

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Productinfo

Type

• Project Management Software

Vendor

• ZephyrProject

Name

• Zephyr

Version

• 4.4.0
• 4.4.1

CPE 2.3info

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CPE 2.2info

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