A security researcher disclosed a Windows 10 zero-day vulnerability involving a local privilege escalation that could enable malicious actors to take over a computer and act as an administrator.

In a posting on GitHub, a developer known as SandboxEscaper published details on how to get around a Microsoft patch for CVE-2019-0841, a bug that allows cybercriminals to overwrite permissions on targeted files owned by NT AUTHORITY\SYSTEM and effectively hijack them.

Although the Windows 10 zero-day wouldn’t allow rogue third parties to break into a system, it would give them “full control” once inside, the researcher suggested. This could include viewing and deleting files, installing applications and other activities.

How the Windows 10 Zero-Day Vulnerability Works

Using Microsoft’s own Edge browser — though other browsers could also work, according to the developer — threat actors could use their normal user privileges to access and delete a set of files. This would cause Edge to crash, but once relaunched, the actors could then impersonate the SYSTEM account by rewriting its discretionary access control list (DACL). In some cases, the malicious actors may need to launch the browser several times and use the desktop shortcut or taskbar button for the trick to work.

The process of discovering the local privilege escalation and writing a proof of concept was completed in a matter of only two hours, according to the Github posting. Another security researcher shared a video showing exactly how the proof of concept works on Twitter.

Protect Yourself With Watchlists, Pen Testing and Vulnerability Scans

Organizations have been becoming more diligent about applying patches as soon as they are released. The latest means to bypass the fix for CVE-2019-0841, however, shows how quickly things can change in threat actors’ favor.

IBM experts suggest signing up for free watchlists that provide information about zero-day threats the moment they become available and help assess whether your organization will be affected. Security teams should also invest in penetration testing and vulnerability scanning services to remediate zero-day vulnerabilities before malicious actors have a chance to exploit them.