CVE-2020-37063: TFTP Turbo Privilege Escalation Flaw

CVE-2020-37063 Overview

CVE-2020-37063 is an unquoted service path vulnerability affecting TFTP Turbo version 4.6.1273. This vulnerability allows local attackers to potentially execute arbitrary code with elevated privileges by exploiting the unquoted path in the Windows service configuration. When the TFTP Turbo service starts, Windows may execute a malicious executable placed in a directory along the unquoted path instead of the intended service binary, granting attackers LocalSystem permissions.

Critical Impact

Local privilege escalation to LocalSystem permissions through unquoted service path exploitation, enabling complete system compromise.

Affected Products

• TFTP Turbo 4.6.1273
• Potentially other versions of TFTP Turbo with unquoted service paths

Discovery Timeline

• 2026-02-01 - CVE CVE-2020-37063 published to NVD
• 2026-02-03 - Last updated in NVD database

Technical Details for CVE-2020-37063

Vulnerability Analysis

This vulnerability falls under 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. Windows interprets unquoted paths with spaces by attempting to execute files at each space-delimited segment of the path before reaching the intended executable.

For example, if the TFTP Turbo service is installed with an unquoted path such as C:\Program Files\TFTP Turbo\service.exe, Windows will attempt to execute in the following order:

1. C:\Program.exe
2. C:\Program Files\TFTP.exe
3. C:\Program Files\TFTP Turbo\service.exe

This behavior allows an attacker with local write access to strategically place a malicious executable (e.g., C:\Program Files\TFTP.exe) that will be executed with the service's elevated privileges instead of the legitimate binary.

Root Cause

The root cause is improper service registration during TFTP Turbo installation. The installer fails to enclose the service executable path in quotation marks when registering the Windows service. This oversight creates an exploitable path resolution ambiguity that Windows Service Control Manager (SCM) follows when starting the service.

Attack Vector

The attack requires local access to the target system with sufficient write permissions to place a malicious executable in one of the intermediate path locations. The attack flow involves:

1. Identifying the unquoted service path in the Windows registry or via sc qc command
2. Placing a malicious executable at a path location that Windows will resolve before the legitimate binary
3. Waiting for the service to restart or triggering a service restart
4. The malicious code executes with LocalSystem privileges

The vulnerability exploitation does not require user interaction and can be triggered during system boot or manual service restart. Since TFTP Turbo services typically run as LocalSystem, successful exploitation grants the attacker complete control over the compromised system.

Detection Methods for CVE-2020-37063

Indicators of Compromise

• Unexpected executables in C:\Program Files\ directory with names like TFTP.exe or similar partial path names
• Unusual processes spawning from service startup with LocalSystem privileges
• Modifications to directories along the TFTP Turbo installation path
• Registry changes to the TFTP Turbo service ImagePath value

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 common exploitation directories such as C:\Program.exe or C:\Program Files\TFTP.exe
• Implement application whitelisting to prevent unauthorized executables from running
• Use SentinelOne's behavioral AI to detect anomalous process execution patterns during service startup

Monitoring Recommendations

• Enable Windows Event logging for service start/stop events (Event ID 7045, 7036)
• Configure file integrity monitoring on directories commonly targeted by unquoted path attacks
• Monitor for new executable files being created in C:\ or C:\Program Files\ root directories
• Implement SentinelOne's real-time monitoring to detect privilege escalation attempts

How to Mitigate CVE-2020-37063

Immediate Actions Required

• Audit the TFTP Turbo service path using sc qc "TFTP Turbo" or registry inspection
• Manually correct the service ImagePath by adding quotation marks around the executable path
• Remove any suspicious executables from intermediate path locations
• Consider disabling the TFTP Turbo service until the path is corrected

Patch Information

No official vendor patch information is currently available. Organizations should manually remediate by correcting the service path configuration. Additional technical details and proof-of-concept information can be found at Exploit-DB #48085 and the VulnCheck Advisory. The vendor's homepage is available at Weird Solutions.

Workarounds

• Manually edit the service ImagePath in the Windows registry to include quotation marks: HKLM\SYSTEM\CurrentControlSet\Services\<ServiceName>\ImagePath
• Use the sc config command to update the service path with proper quoting
• Restrict write permissions on directories along the service path to prevent malicious file placement
• Implement application control policies to block unauthorized executables

# Configuration example - Fix unquoted service path
# Check current service path
sc qc "TFTP Turbo"

# Correct the path with quotation marks (adjust path as needed)
sc config "TFTP Turbo" binPath= "\"C:\Program Files\TFTP Turbo\TFTPTurbo.exe\""

# Verify the fix was applied
sc qc "TFTP Turbo"