A newly disclosed technique demonstrates how Windows’ built-in Private Character Editor (eudcedit.exe) can be exploited to bypass User Account Control (UAC) and escalate privileges without user interaction, posing a serious risk for enterprise environments. Originally designed to allow users to create and edit End-User Defined Characters (EUDC) for custom fonts, the utility resides in C:\Windows\System32 and appears harmless. However, security researcher has shown that it can be turned into a privilege escalation tool, raising concerns among system administrators worldwide.

The root of the vulnerability lies in eudcedit.exe’s application manifest, which contains two key configurations: <requestedExecutionLevel level="requireAdministrator" />, forcing the binary to run with administrative rights, and <autoElevate>true</autoElevate>, enabling silent elevation without UAC prompts for trusted processes when executed by administrators. When UAC is set to permissive modes such as “Elevate without prompting,” Windows will automatically raise eudcedit.exe’s integrity from Medium to High without notifying the user, effectively granting elevated privileges instantly.

The attack method is straightforward yet highly effective. Once launched, eudcedit.exe automatically runs with elevated privileges. An attacker can then access its font linking function via the File menu. At the point where the program prompts to save a file, the elevated process can be hijacked to run arbitrary commands. Simply typing “PowerShell” into the file dialog spawns a fully privileged PowerShell session that inherits the elevated integrity level of the parent process providing attackers with unrestricted system access.

Microsoft has historically maintained that UAC is a convenience feature rather than a robust security boundary, meaning such bypass techniques rarely receive official patches. This case underscores how legitimate system utilities, when combined with permissive configurations, can be weaponized for malicious purposes. The eudcedit.exe bypass not only highlights weaknesses in Windows privilege elevation mechanisms but also reinforces the need for strict UAC policies, application control measures, and user awareness to mitigate exploitation.