CVE-2021-47810: WibuKey Runtime Privilege Escalation Flaw

CVE-2021-47810 Overview

CVE-2021-47810 is an unquoted service path vulnerability affecting WibuKey Runtime 6.51. The vulnerability exists in the WkSvW32.exe service, where the service executable path is not properly quoted. This security flaw allows local attackers to potentially execute arbitrary code by placing a malicious executable in a location that Windows will execute before the legitimate service binary.

The unquoted path C:\PROGRAM FILES (X86)\WIBUKEY\SERVER\WkSvW32.exe contains spaces, which Windows interprets as potential command separators. This creates an opportunity for privilege escalation when an attacker with local access places a specially crafted executable in a predictable location along the path.

Critical Impact

Local attackers can exploit this unquoted service path to inject malicious executables and escalate privileges to SYSTEM level, potentially gaining complete control over the affected system.

Affected Products

• WibuKey Runtime version 6.51
• WkSvW32.exe service component
• Windows-based systems with WibuKey Runtime installed

Discovery Timeline

• 2026-01-16 - CVE CVE-2021-47810 published to NVD
• 2026-01-16 - Last updated in NVD database

Technical Details for CVE-2021-47810

Vulnerability Analysis

This vulnerability is classified under CWE-428 (Unquoted Search Path or Element). When a Windows service is configured with an executable path that contains spaces and is not enclosed in quotation marks, the operating system's path resolution mechanism can be exploited.

In the case of WibuKey Runtime, the service path C:\PROGRAM FILES (X86)\WIBUKEY\SERVER\WkSvW32.exe is registered without proper quoting. Windows attempts to resolve this path by trying multiple combinations before finding the correct executable. This behavior creates a race condition where an attacker can place a malicious binary at one of these intermediate path locations.

The vulnerability requires local access and low privileges to exploit, but a successful attack can result in complete compromise of confidentiality, integrity, and availability on the local system.

Root Cause

The root cause is the improper handling of the service executable path during installation or service registration. The Windows Service Control Manager interprets unquoted paths containing spaces as potentially multiple arguments. When the service starts, Windows sequentially attempts to execute:

1. C:\PROGRAM.exe
2. C:\PROGRAM FILES.exe
3. C:\PROGRAM FILES (X86)\WIBUKEY\SERVER\WkSvW32.exe

If an attacker can write to C:\ or C:\PROGRAM FILES (X86)\, they can place a malicious executable that Windows will execute with the privileges of the service account (typically SYSTEM).

Attack Vector

The attack vector is local, requiring the attacker to have authenticated access to the target system. The attack sequence involves:

1. Identifying the vulnerable unquoted service path in the Windows registry or via service enumeration tools
2. Verifying write permissions to one of the intermediate path locations
3. Placing a malicious executable named appropriately (e.g., Program.exe in C:\)
4. Waiting for or triggering a service restart to execute the malicious payload
5. The malicious code executes with elevated privileges, typically SYSTEM

The exploitation mechanism relies on Windows' path parsing behavior, which is a well-documented attack pattern. For detailed technical information, see the VulnCheck Security Advisory and Exploit-DB #49999.

Detection Methods for CVE-2021-47810

Indicators of Compromise

• Presence of unexpected executables named Program.exe, PROGRAM FILES.exe, or similar in C:\ or parent directories
• Unusual process creation events with parent process being services.exe or WkSvW32.exe
• Modified timestamps on executables in paths along the unquoted service path
• Unexpected service startup failures followed by successful execution from alternate locations

Detection Strategies

• Query Windows services for unquoted paths containing spaces using PowerShell: Get-WmiObject win32_service | Where-Object {$_.PathName -notlike '"*"' -and $_.PathName -like '* *'}
• Monitor file creation events in root directories and common exploitation paths
• Implement application whitelisting to prevent unauthorized executable execution
• Use SentinelOne's behavioral AI to detect anomalous process execution patterns from service contexts

Monitoring Recommendations

• Enable Windows Security Event logging for service control manager events (Event IDs 7000, 7009, 7045)
• Monitor for file writes to C:\Program.exe, C:\Program Files.exe, and similar paths
• Track process creation events where the parent is a Windows service running as SYSTEM
• Configure alerts for new executable files appearing in system root directories

How to Mitigate CVE-2021-47810

Immediate Actions Required

• Audit all Windows services for unquoted paths using the detection query provided above
• Restrict write permissions on C:\ and other root directories to administrators only
• Implement application control policies to prevent unauthorized executable execution
• Monitor for exploitation attempts using endpoint detection solutions

Patch Information

Users should check for updated versions of WibuKey Runtime from the vendor. Visit the Wibu User Software Downloads page for the latest security updates. Additionally, review the VulnCheck Security Advisory for detailed remediation guidance.

Workarounds

• Manually correct the service path by adding quotation marks around the executable path in the Windows registry
• Restrict NTFS permissions on directories along the service path to prevent write access by non-administrators
• Implement application whitelisting to block unauthorized executables from running
• Use Group Policy to enforce service path security configurations across enterprise environments

# Registry fix to quote the service path (run as Administrator)
# Backup the registry first before making changes
reg query "HKLM\SYSTEM\CurrentControlSet\Services\WkSvW32" /v ImagePath
reg add "HKLM\SYSTEM\CurrentControlSet\Services\WkSvW32" /v ImagePath /t REG_EXPAND_SZ /d "\"C:\PROGRAM FILES (X86)\WIBUKEY\SERVER\WkSvW32.exe\"" /f