CVE-2020-37199: NBMonitor DoS Vulnerability

CVE-2020-37199 Overview

CVE-2020-37199 is a buffer overflow vulnerability (CWE-120) affecting NBMonitor version 1.6.6.0. The vulnerability exists in the application's registration key input functionality and allows attackers to crash the application by supplying an oversized buffer payload. Specifically, attackers can generate a 1000-character buffer and paste it into the 'Key' field to trigger an application crash, resulting in a denial of service condition.

Critical Impact

Local attackers can cause application crashes through buffer overflow in the registration key input field, disrupting monitoring capabilities and potentially impacting network visibility.

Affected Products

• NBMonitor version 1.6.6.0
• NSA Auditor Tool Suite (related product from same vendor)

Discovery Timeline

• 2026-02-11 - CVE CVE-2020-37199 published to NVD
• 2026-02-12 - Last updated in NVD database

Technical Details for CVE-2020-37199

Vulnerability Analysis

This vulnerability is classified as CWE-120 (Buffer Copy without Checking Size of Input), commonly known as a classic buffer overflow. The flaw exists in how NBMonitor handles user input in the registration key validation routine. When processing the 'Key' field input, the application fails to properly validate the length of the supplied data before copying it into a fixed-size buffer.

The local attack vector requires user interaction, meaning an attacker would need to either have direct access to the system or convince a user to paste malicious input into the key field. The vulnerability results in application availability impact without affecting confidentiality or integrity of the system.

Root Cause

The root cause is improper input validation in the registration key processing function. The application allocates a fixed-size buffer to store the registration key but does not implement proper bounds checking before copying user-supplied data. When input exceeding the buffer's capacity (approximately 1000 characters) is provided, it overwrites adjacent memory, causing the application to crash.

Attack Vector

The attack requires local access to the NBMonitor application. An attacker must craft a payload of approximately 1000 characters and input it into the 'Key' registration field. This can be accomplished by:

1. Generating a buffer of 1000+ characters (any character pattern)
2. Opening the NBMonitor application's registration dialog
3. Pasting the oversized buffer into the Key input field
4. The application crashes due to buffer overflow

The vulnerability is documented in Exploit-DB #47866, which provides proof-of-concept details for triggering the denial of service condition.

Detection Methods for CVE-2020-37199

Indicators of Compromise

• Unexpected NBMonitor application crashes or restarts
• Windows Event Log entries indicating application crashes for NBMonitor.exe
• Crash dump files generated in the Windows crash dump directory related to NBMonitor
• User reports of application instability when interacting with registration functionality

Detection Strategies

• Monitor application crash events using Windows Event Viewer filtering for NBMonitor process terminations
• Implement endpoint detection rules to alert on repeated application crashes from the same process
• Use SentinelOne's behavioral AI to detect anomalous application termination patterns
• Review system crash dumps for buffer overflow indicators in NBMonitor memory space

Monitoring Recommendations

• Enable detailed application logging for NBMonitor where available
• Configure endpoint detection and response (EDR) solutions to track application stability metrics
• Set up alerts for multiple consecutive crashes of monitoring tools that could indicate exploitation attempts
• Maintain visibility into user interactions with registration interfaces through session recording where permitted

How to Mitigate CVE-2020-37199

Immediate Actions Required

• Restrict access to the NBMonitor application to authorized personnel only
• Consider replacing NBMonitor 1.6.6.0 with alternative network monitoring solutions if a patched version is not available
• Implement application whitelisting to prevent unauthorized execution of the vulnerable software
• Review and limit user access to the registration functionality until remediation is complete

Patch Information

No vendor patch information is available at this time. The VulnCheck Denial of Service Advisory and NSA Auditor Tool website should be monitored for updates regarding security fixes. Organizations should contact the vendor directly to inquire about patched versions.

Workarounds

• Disable or restrict access to the registration key input functionality if registration is already complete
• Run NBMonitor in a sandboxed environment to contain potential crashes and limit impact
• Implement network segmentation to ensure that denial of service against monitoring tools doesn't impact critical security functions
• Deploy redundant monitoring solutions to maintain visibility if NBMonitor becomes unavailable