CVE-2021-47780: Macro Expert Privilege Escalation Flaw

CVE-2021-47780 Overview

CVE-2021-47780 is an unquoted service path vulnerability in Macro Expert version 4.7 that allows local users to potentially execute arbitrary code with elevated system privileges. This vulnerability arises from improperly configured Windows service paths that lack quotation marks around paths containing spaces. Attackers with local access can exploit this misconfiguration to inject malicious executables that will be executed with LocalSystem permissions during service startup.

Critical Impact

Local attackers can achieve privilege escalation to SYSTEM-level permissions by placing a malicious executable in the unquoted service path, potentially leading to complete system compromise.

Affected Products

• Macro Expert version 4.7
• Macro-expert Macro Expert (all builds of version 4.7)

Discovery Timeline

• 2026-01-16 - CVE CVE-2021-47780 published to NVD
• 2026-01-21 - Last updated in NVD database

Technical Details for CVE-2021-47780

Vulnerability Analysis

The unquoted service path vulnerability (CWE-428) in Macro Expert 4.7 stems from the Windows service configuration not properly enclosing the executable path in quotation marks. When a Windows service path contains spaces and is not enclosed in quotes, the Windows Service Control Manager (SCM) parses the path ambiguously, attempting to locate and execute binaries at each space-delimited segment of the path.

For example, if the service path is configured as C:\Program Files\Macro Expert\MacroExpert.exe, Windows will attempt to execute files in the following order:

1. C:\Program.exe
2. C:\Program Files\Macro.exe
3. C:\Program Files\Macro Expert\MacroExpert.exe

This parsing behavior creates an opportunity for attackers to place a malicious executable (such as Macro.exe) in the C:\Program Files\ directory, which would be executed with the service's privileges—typically LocalSystem—before the legitimate service binary.

Root Cause

The root cause of this vulnerability is the failure to properly quote the service executable path during the installation of Macro Expert 4.7. The Windows registry entry for the service's ImagePath value contains an unquoted path with spaces, enabling the path traversal exploitation technique. This is a common misconfiguration that occurs when software installers do not follow secure coding practices for Windows service registration.

Attack Vector

This vulnerability requires local access to the target system. An attacker must have write permissions to one of the directories in the unquoted path (such as C:\Program Files\) to place a malicious executable. The attack is executed when the vulnerable service is started or restarted, at which point the malicious binary is executed with elevated LocalSystem privileges.

The exploitation process involves:

1. Identifying the unquoted service path in the Windows registry
2. Crafting a malicious executable payload
3. Placing the executable at an interceptable location in the service path
4. Waiting for or triggering a service restart to execute the payload with SYSTEM privileges

Technical details and proof-of-concept information are available in the Exploit-DB #50431 advisory.

Detection Methods for CVE-2021-47780

Indicators of Compromise

• Unexpected executable files in C:\Program Files\ or other directories along the service path (e.g., Program.exe, Macro.exe)
• Unauthorized modifications to the Windows Service registry keys for Macro Expert
• Process execution anomalies showing unfamiliar binaries running under LocalSystem context
• New or modified files in system directories with timestamps correlating to service startup events

Detection Strategies

• Query Windows services for unquoted paths using PowerShell: Get-WmiObject Win32_Service | Where-Object { $_.PathName -notlike '"*' -and $_.PathName -like '* *' }
• Monitor file creation events in directories commonly exploited by unquoted service path attacks
• Implement application whitelisting to prevent execution of unauthorized binaries
• Use endpoint detection tools to identify privilege escalation attempts and suspicious process lineage

Monitoring Recommendations

• Enable Windows Security Event logging for service start events (Event ID 7035, 7036)
• Configure file integrity monitoring on critical system directories including C:\Program Files\
• Implement process creation auditing to detect unexpected processes running under SYSTEM context
• Deploy SentinelOne agents with behavioral AI to identify and block malicious payload execution during service startup

How to Mitigate CVE-2021-47780

Immediate Actions Required

• Audit all installed services for unquoted paths using the PowerShell detection command
• Manually remediate the Macro Expert service path by adding quotation marks to the registry entry
• Remove any suspicious executables found in directories along the service path
• Restrict write permissions on directories commonly targeted by this attack vector (e.g., C:\Program Files\)
• Consider uninstalling Macro Expert 4.7 until an official patch is available

Patch Information

At the time of publication, no official vendor patch has been released for this vulnerability. Users should contact Macro Expert support for remediation guidance or implement the manual registry fix described below. Monitor the Macro Expert Homepage for security updates and the VulnCheck Advisory for additional information.

Workarounds

• Manually quote the service path in the Windows registry by modifying the ImagePath value under HKLM\SYSTEM\CurrentControlSet\Services\[ServiceName]
• Implement strict access controls on directories in the service path to prevent unauthorized file creation
• Use Windows Defender Application Control (WDAC) or AppLocker to restrict executable execution to approved binaries
• Deploy endpoint protection solutions like SentinelOne to detect and prevent exploitation attempts in real-time

# Registry fix to quote the service path (run as Administrator)
# First, backup the current registry value, then update with quoted path
reg query "HKLM\SYSTEM\CurrentControlSet\Services\MacroExpertService" /v ImagePath
reg add "HKLM\SYSTEM\CurrentControlSet\Services\MacroExpertService" /v ImagePath /t REG_EXPAND_SZ /d "\"C:\Program Files\Macro Expert\MacroExpert.exe\"" /f