CVE-2016-20061: Sheed AntiVirus Privilege Escalation Flaw

CVE-2016-20061 Overview

CVE-2016-20061 is an unquoted service path vulnerability affecting sheed AntiVirus 2.3. The vulnerability exists in the ShavProt service, which improperly handles the service binary path by failing to enclose it in quotation marks. This configuration flaw allows local attackers with low privileges to escalate their access to LocalSystem privileges by placing a malicious executable in the unquoted path.

Critical Impact

Local attackers can achieve complete system compromise by exploiting this privilege escalation vulnerability to execute arbitrary code with LocalSystem privileges.

Affected Products

• sheed AntiVirus 2.3
• ShavProt service component

Discovery Timeline

• 2026-04-04 - CVE CVE-2016-20061 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2016-20061

Vulnerability Analysis

This vulnerability falls under CWE-428 (Unquoted Search Path or Element), a well-documented Windows service misconfiguration. When a Windows service executable path contains spaces and is not enclosed in quotation marks, Windows attempts to locate the executable by testing multiple path combinations during service startup. An attacker with write access to directories in the service path can exploit this behavior to execute malicious code with the privileges of the service account.

The ShavProt service in sheed AntiVirus 2.3 runs with LocalSystem privileges, making successful exploitation particularly dangerous. LocalSystem is the highest privilege level on a Windows system, providing complete control over the operating system and all installed software.

Root Cause

The root cause of this vulnerability is improper service installation configuration. When the ShavProt service was registered with Windows, the path to the service executable was not enclosed in quotation marks. This is a common oversight during software development, particularly when installation paths contain spaces (such as C:\Program Files\).

Windows services with unquoted paths containing spaces allow the operating system to interpret the path ambiguously, creating opportunities for path hijacking attacks.

Attack Vector

The attack requires local access to the target system and the ability to write files to specific directories within the unquoted service path. The attack sequence involves:

1. Identifying the unquoted service path for ShavProt
2. Determining writable locations within the path where Windows will attempt to locate executables
3. Placing a malicious executable (e.g., Program.exe in C:\) that will be executed before the legitimate service binary
4. Triggering service restart through system reboot or service manipulation

When the system restarts or the service is restarted, Windows will locate and execute the attacker's malicious binary with LocalSystem privileges instead of the intended service executable.

Detection Methods for CVE-2016-20061

Indicators of Compromise

• Unexpected executables in root directories or within Program Files paths (e.g., C:\Program.exe, C:\Program Files\Sheed.exe)
• Unusual processes running with SYSTEM privileges that do not match expected system binaries
• Service start failures followed by suspicious process execution
• Modified file system timestamps in directories along the service path

Detection Strategies

• Use Windows Management Instrumentation (WMI) or PowerShell to query for services with unquoted paths containing spaces: Get-WmiObject Win32_Service | Where-Object { $_.PathName -notmatch '^"' -and $_.PathName -match ' ' }
• Implement file integrity monitoring on directories commonly targeted by unquoted path attacks
• Monitor Windows Event Log for service start failures (Event ID 7000, 7009) correlated with process creation events
• Deploy endpoint detection rules to identify new executable files created in suspicious locations

Monitoring Recommendations

• Enable process creation auditing (Event ID 4688) with command line logging to track service-related process executions
• Configure alerts for file creation events in root directories and common unquoted path locations
• Monitor for unusual service restarts or configuration changes to the ShavProt service
• Implement behavioral analytics to detect privilege escalation patterns

How to Mitigate CVE-2016-20061

Immediate Actions Required

• Audit the ShavProt service path using sc qc ShavProt command to verify the unquoted path condition
• Restrict write permissions on directories within the service path to prevent unauthorized file placement
• Consider temporarily disabling or uninstalling sheed AntiVirus 2.3 if the software is no longer maintained
• Implement application whitelisting to prevent unauthorized executables from running

Patch Information

No official vendor patch information is available for this vulnerability. The Sheed Antivirus homepage and VulnCheck Advisory may provide additional guidance. Technical details are also available in Exploit-DB #40497.

Workarounds

• Manually fix the service path by modifying the registry key at HKLM\SYSTEM\CurrentControlSet\Services\ShavProt and enclosing the ImagePath value in quotation marks
• Restrict NTFS permissions on C:\ and C:\Program Files\ directories to prevent non-administrator users from creating new files
• Deploy endpoint protection solutions capable of detecting and blocking unquoted service path exploitation attempts
• Consider migrating to an actively maintained antivirus solution with proper security controls

# Configuration example
# Fix unquoted service path via registry (run as Administrator)
# Backup current value first, then update ImagePath to include quotes
reg query "HKLM\SYSTEM\CurrentControlSet\Services\ShavProt" /v ImagePath
# Example fix command (adjust path as needed):
# reg add "HKLM\SYSTEM\CurrentControlSet\Services\ShavProt" /v ImagePath /t REG_EXPAND_SZ /d "\"C:\Program Files\Sheed AntiVirus\ShavProt.exe\"" /f