CVE-2021-47790: Active WebCam Privilege Escalation Flaw

CVE-2021-47790 Overview

Active WebCam 11.5 contains an unquoted service path vulnerability that allows local attackers to execute arbitrary code with elevated system privileges. Attackers can exploit the misconfigured service path by placing malicious executables in specific directory locations to gain administrative access.

Critical Impact

Local attackers can achieve privilege escalation to SYSTEM level by exploiting the unquoted service path, potentially leading to full system compromise.

Affected Products

• Active WebCam 11.5

Discovery Timeline

• 2026-01-16 - CVE CVE-2021-47790 published to NVD
• 2026-01-16 - Last updated in NVD database

Technical Details for CVE-2021-47790

Vulnerability Analysis

This vulnerability is classified as CWE-428 (Unquoted Search Path or Element), a configuration flaw that occurs when a Windows service executable path contains spaces but is not enclosed in quotation marks. When Windows attempts to start a service with an unquoted path containing spaces, it interprets each space as a potential delimiter, attempting to execute files at each parsed location before reaching the intended executable.

For example, if Active WebCam's service is registered with a path like C:\Program Files\Active WebCam\service.exe, Windows will attempt to execute in the following order: C:\Program.exe, C:\Program Files\Active.exe, and finally the intended executable. An attacker with write access to any of these intermediate locations can place a malicious executable that will be run with the service's privileges—typically SYSTEM.

Root Cause

The root cause of this vulnerability lies in improper service registration within Active WebCam 11.5. During installation, the software registers its Windows service with an executable path that contains spaces but omits the required quotation marks. This misconfiguration creates an opportunity for local privilege escalation when combined with write access to directories earlier in the path resolution order.

Attack Vector

This is a local attack vector requiring the attacker to have authenticated access to the target system. The attacker must also have write permissions to one of the directories parsed during the unquoted path resolution process. Common attack scenarios include:

1. An attacker with low-privileged user access identifies the vulnerable service using tools like wmic or PowerShell
2. The attacker places a malicious executable (e.g., Active.exe) in the C:\Program Files\ directory
3. When the service restarts (either manually triggered, during system reboot, or through service crash), Windows executes the malicious payload with SYSTEM privileges
4. The attacker gains full administrative control over the system

The exploitation does not require user interaction beyond the initial placement of the malicious executable, and persistence is achieved through the service's automatic startup behavior.

Detection Methods for CVE-2021-47790

Indicators of Compromise

• Unexpected executable files in C:\Program Files\ directory with names like Active.exe or Program.exe
• Unusual service behavior or restarts for Active WebCam related services
• New processes spawning from service accounts with unexpected parent-child relationships
• File creation events in directories along the service path from non-administrative accounts

Detection Strategies

• Use PowerShell or wmic commands to audit all services with unquoted paths: wmic service get name,displayname,pathname,startmode | findstr /i "auto" | findstr /i /v "c:\windows\\" | findstr /i /v """
• Deploy endpoint detection rules to monitor for executable file creation in C:\Program Files\ root directory
• Implement file integrity monitoring on directories commonly targeted by unquoted path attacks
• Monitor Windows Event Logs for Service Control Manager events (Event ID 7045) indicating new service installations

Monitoring Recommendations

• Configure SentinelOne Singularity to detect and alert on suspicious executable placement in system directories
• Enable behavioral analysis to identify processes spawned from services with unusual characteristics
• Monitor for privilege escalation attempts involving Windows services
• Regularly audit service configurations for unquoted paths using automated scanning tools

How to Mitigate CVE-2021-47790

Immediate Actions Required

• Audit Active WebCam 11.5 installations and verify service path configurations
• Manually correct the service path by adding quotation marks around the executable path in the Windows Registry
• Restrict write permissions on directories that could be exploited (e.g., C:\Program Files\)
• Consider uninstalling Active WebCam if it is no longer required or if no vendor patch is available

Patch Information

No official vendor patch has been confirmed for this vulnerability. The vendor (Pysoft) should be contacted directly via their official website for remediation guidance. Additional technical details and exploit information can be found in the Exploit-DB #50273 advisory and the VulnCheck Advisory.

Workarounds

• Manually fix the unquoted service path by modifying the ImagePath value in the Windows Registry under HKLM\SYSTEM\CurrentControlSet\Services\[ServiceName] to include quotation marks
• Implement application whitelisting to prevent unauthorized executables from running in sensitive directories
• Apply the principle of least privilege to limit user write access to system directories
• Use Group Policy to restrict service modifications and executable installations
• Consider migrating to alternative webcam software with better security practices

# Configuration example - Fix unquoted service path via registry
# PowerShell command to identify and remediate unquoted service paths

# Identify vulnerable services
Get-WmiObject Win32_Service | Where-Object { 
    $_.PathName -notmatch '^"' -and 
    $_.PathName -match ' ' -and 
    $_.PathName -notmatch '^C:\\Windows\\'
} | Select-Object Name, PathName

# Manual fix in registry (run as Administrator)
# Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\ActiveWebCam" -Name "ImagePath" -Value '"C:\Program Files\Active WebCam\service.exe"'