Windows User Account Control Bypassed Using Character Editor to Escalate Privileges

A sophisticated new technique that exploits the Windows Private Character Editor to bypass User Account Control (UAC) and achieve privilege escalation without user intervention, raising significant concerns for system administrators worldwide.

The attack disclosed by Matan Bahar leverages eudcedit.exeMicrosoft’s built-in Private Character Editor, located in C:\Windows\System32, which was originally designed to create and edit End-User Defined Characters (EUDC).

These custom characters allow users to create personalized glyphs mapped to Unicode code points for use in documents and applications. However, security researchers have discovered that this seemingly benign utility can be weaponized to bypass Windows’ primary security gatekeeper.

Windows User Account Control Bypassed

The vulnerability stems from critical configurations embedded within eudcedit.exe’s application manifest. Two specific metadata tags create the security loophole:

• <requestedExecutionLevel level="requireAdministrator" /> – Instructs Windows to run the binary with full administrative privileges
• <autoElevate>true</autoElevate> – Enables automatic elevation without UAC prompts for trusted binaries when executed by users in the Administrators group.

This combination proves particularly dangerous. When UAC is configured with permissive settings such as “Elevate without prompting,” Windows automatically elevates eudcedit.exe from Medium to High integrity without displaying any security warnings, Bahar said.

The attack unfolds through a carefully crafted sequence that exploits the application’s file handling mechanisms. Attackers begin by launching the Private Character Editor, which automatically elevates to High integrity.

They then navigate to the font linking functionality within the application interface, typically accessed through the File menu.

The critical vulnerability manifests when users select font linking options and are prompted to save files. At this juncture, the elevated eudcedit.exe process can be manipulated to execute arbitrary commands.

By simply entering “PowerShell” in the file dialog, attackers can spawn a high-privilege PowerShell session that inherits the elevated integrity level of the parent process.

Microsoft’s approach to UAC bypasses remains consistent with historical patterns. Since UAC is designed as a convenience feature rather than a security boundary, the company typically does not issue patches for bypass techniques.

The eudcedit.exe UAC bypass demonstrates how attackers can weaponize legitimate system utilities to achieve malicious objectives. This technique’s simplicity and effectiveness make it a significant concern for enterprise security teams.

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