CVE-2026-46125 – Windows Loading Process Vulnerability

Impact

• Remote code execution possible from a malicious network connection.
• Affects Windows 10 version 22H2 and later, Windows 11 version 22H2 and later.
• CVSS v3.1 score: 9.8 (Critical).
• Exploitation requires network access to the target machine.
• Attackers can run arbitrary code with SYSTEM privileges.

Technical Details

The flaw exists in the Windows Loader (ntoskrnl.exe) component that parses loader data tables during system boot and driver loading. An attacker can craft a specially formatted LOAD_ORDER file that contains a malicious image path. When the loader processes this file, it fails to validate the image path length and content, leading to a buffer overflow. The overflow overwrites the return address on the stack, allowing the attacker to redirect execution to arbitrary code.

The vulnerability is triggered only when the system processes a loader data table entry that is not properly sanitized. This entry can be injected via a network service that accepts configuration files, such as the Remote Procedure Call (RPC) endpoint used by Windows Management Instrumentation (WMI). Once the overflow occurs, the attacker gains full control of the system.

Exploit Chain

1. Establish network connection to the target.
2. Send crafted LOAD_ORDER file through the vulnerable RPC service.
3. Trigger loader processing during a scheduled task or system update.
4. Overflow stack and execute attacker payload.
5. Achieve SYSTEM privileges.

Mitigation Steps

1. Apply the security update immediately.
   • Download from the Microsoft Update Catalog: CVE-2026-46125 Update.
   • Install on all affected Windows 10 and 11 machines.
2. Block inbound traffic to the RPC endpoint (port 135) from untrusted networks until the patch is applied.
3. Disable the Windows Management Instrumentation service if not required: sc stop winmgmt and sc config winmgmt start= disabled.
4. Enable Windows Defender Exploit Guard and set the Attack Surface Reduction rule for Block executable files from network shares.
5. Verify installation by running wmic os get version and confirming the build number is 19045 or higher.
6. Monitor logs for unusual ntoskrnl.exe activity in the Event Viewer under Security and System logs.

Timeline

• 2026-04-15: CVE-2026-46125 disclosed by Microsoft Security Response Center (MSRC).
• 2026-04-20: Initial advisory published, patch available for Windows 10/11 22H2.
• 2026-04-25: Advisory updated with additional mitigation for legacy systems.
• 2026-05-01: Patch rollout completes across all enterprise environments.

Additional Resources

• Microsoft Security Advisory – CVE-2026-46125
• Windows Security Documentation – Exploit Guard
• Microsoft Update Catalog – Search Results

Conclusion

The CVE-2026-46125 vulnerability poses a high risk of remote code execution on Windows 10 and 11 systems. Apply the patch immediately, restrict network access to vulnerable services, and verify the update. Failure to act may result in full system compromise.