CVE-2020-37025: Port Forwarding Wizard Buffer Overflow

CVE-2020-37025 Overview

Port Forwarding Wizard 4.8.0 contains a buffer overflow vulnerability (CWE-120) that allows local attackers to execute arbitrary code through a long request in the Register feature. Attackers can craft a malicious payload with an egg tag and overwrite SEH (Structured Exception Handler) handlers to potentially execute shellcode on vulnerable Windows systems.

Critical Impact

Local attackers can exploit this buffer overflow to achieve arbitrary code execution by overwriting SEH handlers, potentially gaining complete control of the affected Windows system.

Affected Products

• Port Forwarding Wizard version 4.8.0

Discovery Timeline

• 2026-01-30 - CVE CVE-2020-37025 published to NVD
• 2026-02-04 - Last updated in NVD database

Technical Details for CVE-2020-37025

Vulnerability Analysis

This vulnerability is a classic buffer overflow (CWE-120) that occurs when the application fails to properly validate the length of input data in the Register feature. When a user provides an excessively long string as input, the application writes beyond the allocated buffer boundaries, corrupting adjacent memory structures including the SEH chain.

The attack requires local access and user interaction, as the attacker must convince a user to enter or process a maliciously crafted payload. However, once triggered, the vulnerability allows complete control over program execution flow through SEH overwrite techniques commonly used in Windows exploitation.

Root Cause

The root cause is improper input validation in the Register feature of Port Forwarding Wizard. The application allocates a fixed-size buffer for user input but does not implement proper bounds checking before copying data into this buffer. This allows attackers to supply input that exceeds the buffer's capacity, leading to a stack-based buffer overflow condition.

Attack Vector

The attack vector is local, requiring an attacker to have access to the system where Port Forwarding Wizard is installed. The exploitation process involves:

1. Crafting a payload containing an egg tag marker and shellcode
2. Submitting the oversized payload through the Register feature
3. Overflowing the buffer to overwrite the SEH handler addresses on the stack
4. Triggering an exception to transfer execution to the attacker-controlled SEH handler
5. Using egg hunting techniques to locate and execute the shellcode

The SEH overwrite technique is a well-documented exploitation method for bypassing stack protection mechanisms on Windows systems. Additional technical details and a proof-of-concept are available through the Exploit-DB #48695 reference.

Detection Methods for CVE-2020-37025

Indicators of Compromise

• Unusual crashes or exceptions in the Port Forwarding Wizard process (pfwiz.exe)
• Unexpected child processes spawned from the Port Forwarding Wizard application
• Memory access violations or structured exception handling errors in application logs
• Presence of shellcode patterns or NOP sleds in process memory dumps

Detection Strategies

• Monitor for abnormal behavior from the Port Forwarding Wizard process, including unexpected network connections or file system modifications
• Deploy endpoint detection solutions that can identify SEH overwrite attempts and egg-hunting shellcode execution patterns
• Implement application-level logging to capture registration attempts with unusually long input strings
• Use memory integrity monitoring to detect buffer overflow exploitation attempts

Monitoring Recommendations

• Enable Windows Event Logging for application crashes and exceptions related to Port Forwarding Wizard
• Configure SentinelOne's Behavioral AI to alert on suspicious process chains originating from pfwiz.exe
• Monitor for the creation of unexpected executable content in memory regions
• Regularly audit systems for the presence of Port Forwarding Wizard 4.8.0 installations

How to Mitigate CVE-2020-37025

Immediate Actions Required

• Remove or disable Port Forwarding Wizard 4.8.0 from all systems until a patch is available
• Restrict local access to systems running vulnerable installations
• Implement application whitelisting to prevent unauthorized code execution
• Deploy endpoint protection solutions capable of detecting exploitation attempts

Patch Information

No vendor patch information is currently available for this vulnerability. System administrators should monitor the Port Forwarding Wizard website for security updates. The VulnCheck Advisory provides additional guidance on this vulnerability.

Workarounds

• Uninstall Port Forwarding Wizard 4.8.0 and use alternative port forwarding solutions with better security track records
• If removal is not possible, restrict access to the application to trusted users only
• Enable Windows Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) to increase exploitation difficulty
• Consider running the application in an isolated environment or sandbox to limit the impact of potential exploitation

# Windows DEP verification - run in elevated PowerShell
# Check if DEP is enabled system-wide
Get-CimInstance Win32_OperatingSystem | Select-Object DataExecutionPrevention_SupportPolicy

# Verify ASLR settings via registry
reg query "HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management" /v MoveImages