CVE-2021-47805: Disk Savvy Privilege Escalation Flaw

CVE-2021-47805 Overview

CVE-2021-47805 is an unquoted service path vulnerability affecting Disk Savvy 13.6.14, a disk space analysis utility for Windows. The vulnerability exists in the Windows service configuration where the service binary path is not properly enclosed in quotation marks. This configuration flaw allows local attackers to potentially execute arbitrary code by placing a malicious executable in a location that Windows will execute before the intended service binary. Successful exploitation grants the attacker LocalSystem privileges, the highest privilege level on Windows systems.

Critical Impact

Local attackers can achieve privilege escalation to LocalSystem by exploiting the unquoted service path, potentially leading to complete system compromise.

Affected Products

• Flexense Disk Savvy 13.6.14
• Windows installations running vulnerable Disk Savvy service configurations

Discovery Timeline

• 2026-01-16 - CVE CVE-2021-47805 published to NVD
• 2026-01-21 - Last updated in NVD database

Technical Details for CVE-2021-47805

Vulnerability Analysis

The vulnerability is classified under CWE-428 (Unquoted Search Path or Element). When Windows services are configured with executable paths containing spaces that are not properly quoted, the operating system's path resolution mechanism can be abused. Windows parses unquoted paths by attempting to execute progressively longer portions of the path string, checking each combination as a potential executable.

For example, if a service path is configured as C:\Program Files\Disk Savvy\bin\disksavvy.exe, Windows will sequentially attempt to execute:

1. C:\Program.exe
2. C:\Program Files\Disk.exe
3. C:\Program Files\Disk Savvy\bin\disksavvy.exe

An attacker with write access to C:\ or C:\Program Files\ can place a malicious executable named Program.exe or Disk.exe that will be executed with the service's privileges before the legitimate binary runs.

Root Cause

The root cause is improper service registration in the Windows Service Control Manager (SCM). During installation, Disk Savvy 13.6.14 registers its Windows service with an unquoted binary path in the registry under HKLM\SYSTEM\CurrentControlSet\Services\. The service path should be enclosed in double quotation marks to prevent Windows from misinterpreting spaces in the directory structure as argument delimiters.

Attack Vector

The attack requires local access to the system and write permissions to a directory that appears in the truncated path resolution sequence. The attacker must:

1. Identify the unquoted service path in the Windows registry or through service enumeration
2. Determine writable locations in the path resolution chain
3. Place a malicious executable in one of these locations with a filename matching the truncated path component
4. Wait for or trigger a service restart, causing Windows to execute the malicious binary with LocalSystem privileges

The attack is considered local with low complexity, requiring low privileges but no user interaction. While technical details are documented in public advisories, the exploitation requires specific conditions including write access to system directories.

For additional technical information, see the VulnCheck Advisory for DiskSavvy and Exploit-DB #50024.

Detection Methods for CVE-2021-47805

Indicators of Compromise

• Unexpected executable files in C:\ or C:\Program Files\ directories with names like Program.exe or Disk.exe
• Service execution events showing unexpected binary paths being launched under the Disk Savvy service context
• Windows Security Event Log entries (Event ID 4688) showing process creation from anomalous locations with SYSTEM privileges
• Registry modifications to service ImagePath values

Detection Strategies

• Query Windows services for unquoted paths using PowerShell: Get-WmiObject Win32_Service | Where-Object { $_.PathName -notmatch '^"' -and $_.PathName -match ' ' }
• Monitor for new executable files created in root directories and Program Files parent folders
• Implement file integrity monitoring on system directories susceptible to service path hijacking
• Use endpoint detection and response (EDR) solutions to alert on suspicious service binary replacements

Monitoring Recommendations

• Enable Windows Process Creation auditing (Event ID 4688) with command-line logging
• Configure alerts for service binary executions from non-standard installation directories
• Monitor for privilege escalation patterns where low-privileged processes spawn SYSTEM-level children
• Implement SentinelOne's behavioral AI to detect anomalous service execution chains

How to Mitigate CVE-2021-47805

Immediate Actions Required

• Audit all installed services for unquoted paths using the PowerShell detection command above
• Manually quote the Disk Savvy service path in the Windows registry by adding double quotes around the ImagePath value
• Restrict write permissions on C:\ and C:\Program Files\ directories to administrators only
• Consider uninstalling Disk Savvy if not required for business operations until a patched version is available

Patch Information

At the time of this writing, no official patch from Flexense has been documented in the CVE data. Organizations should monitor the DiskSavvy Official Site for security updates. The manual remediation involves correcting the service path registration in the Windows registry.

Workarounds

• Manually edit the registry key at HKLM\SYSTEM\CurrentControlSet\Services\DiskSavvyService to enclose the ImagePath value in quotation marks
• Implement application whitelisting to prevent execution of unauthorized binaries from system directories
• Use Windows Defender Application Control (WDAC) or AppLocker policies to restrict executable launching
• Deploy SentinelOne endpoint protection to detect and prevent exploitation attempts through behavioral analysis

# PowerShell command to fix unquoted service path
# Run as Administrator
$serviceName = "DiskSavvyService"
$regPath = "HKLM:\SYSTEM\CurrentControlSet\Services\$serviceName"
$currentPath = (Get-ItemProperty -Path $regPath -Name ImagePath).ImagePath
if ($currentPath -notmatch '^"') {
    $quotedPath = '"{0}"' -f $currentPath
    Set-ItemProperty -Path $regPath -Name ImagePath -Value $quotedPath
    Write-Host "Service path has been quoted: $quotedPath"
}