CVE-2026-9771 zephyrproject CVE debrief

Who should care

Users and administrators of systems using the Zephyr RTOS with CONFIG_USERSPACE enabled should be aware of this vulnerability and take steps to patch affected systems. This includes operators managing affected deployments, platform administrators, vulnerability management teams, and security teams responsible for monitoring and remediation efforts. Review of system configurations, application of patches, and verification of system integrity are crucial steps in mitigating this vulnerability. Collaboration with vendors for patching and support is also recommended. Affected organizations should prioritize patching based on the vulnerability's severity and potential impact on their operations. This may involve coordinating with vendors, applying patches through change control processes, and verifying the effectiveness of mitigations. Monitoring for exploitation attempts and maintaining awareness of the vulnerability's status are also important for affected parties. The vulnerability's impact on operational security and potential for privilege escalation out of the userspace sandbox highlights the need for prompt action and thorough defensive measures. Therefore, it is essential for all relevant stakeholders to assess their exposure and take appropriate defensive actions to minimize risk. This includes reviewing system configurations, applying patches, and enhancing monitoring and detection capabilities to identify potential exploitation attempts. By taking these steps, organizations can reduce the risk associated with this vulnerability and protect their systems from potential attacks. Additionally, organizations should consider implementing compensating controls for exposed systems while remediation is scheduled and verified, and track exceptions and retest remediated assets to ensure the effectiveness of their defensive measures. This comprehensive approach will help minimize the risk of exploitation and ensure the security of affected systems. The vulnerability's severity and potential impact emphasize the importance of prompt patching and thorough defensive measures to protect against potential attacks. Therefore, affected organizations should prioritize patch

Technical summary

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. A user-mode thread can cause the kernel to call arbitrary code in supervisor mode by supplying a pointer to a forged struct device whose api table contains attacker-chosen function pointers.

Defensive priority

This vulnerability allows for local privilege escalation out of the userspace sandbox, with potential for kernel denial-of-service and information disclosure. Affected systems should prioritize patching.

Recommended defensive actions

• Apply the patch from the Zephyr project repository.
• Review and update affected systems.
• Monitor for potential exploitation attempts.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.

Evidence notes

The vulnerability exists in the flash_copy() system call, verified by z_vrfy_flash_copy() in drivers/flash/flash_util.c. The fix adds K_SYSCALL_DRIVER_FLASH(src_dev, read) and K_SYSCALL_DRIVER_FLASH(dst_dev, write) to z_vrfy_flash_copy(). Evidence is limited to supplied source corpus. Defenders should verify affected systems, review supplied advisories, and monitor for potential exploitation attempts within their environments. Additional information may be necessary for comprehensive risk assessment.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.