system file

A Windows vulnerability named "RegPwn" (CVE-2026-24291) allows low-privileged users to elevate their access to full SYSTEM privileges. Discovered by the MDSec red team, it has been in use since January 2025 and was addressed in a recent Microsoft Patch Tuesday update. The vulnerability exploits the management of Windows accessibility features, which generate a registry key that grants full control to low-privileged users. When a user activates an accessibility tool, the configurations are copied into the local machine registry hive, which remains writable by the logged-in user. This creates an opportunity for manipulation, especially when user-controlled settings interact with the Windows Secure Desktop environment. An attacker can exploit this by modifying their user-level accessibility registry key and using an oplock on a system file, allowing them to replace the local machine registry key with a symbolic link to an arbitrary system registry key. This process operates under SYSTEM privileges, enabling the attacker to write arbitrary values to restricted areas of the Windows registry. MDSec demonstrated this technique to gain access to a SYSTEM-level command prompt. Microsoft has released security updates to address this vulnerability, and MDSec has made the exploit code available on GitHub for research purposes.