CVE-2021-47815: Nsasoft Nsauditor DOS Vulnerability

CVE-2021-47815 Overview

CVE-2021-47815 is a denial of service vulnerability affecting Nsauditor version 3.2.3, a network auditing and monitoring tool developed by Nsasoft. The vulnerability exists in the registration code input field and allows attackers to crash the application by providing malformed input. Specifically, attackers can paste a large buffer of 256 repeated characters into the 'Key' field during software registration, triggering an application crash due to improper input validation.

Critical Impact

This buffer overflow vulnerability enables attackers with local access to reliably crash the Nsauditor application, disrupting network monitoring and auditing capabilities for organizations relying on this tool.

Affected Products

• Nsasoft Nsauditor version 3.2.3

Discovery Timeline

• January 16, 2026 - CVE-2021-47815 published to NVD
• January 21, 2026 - Last updated in NVD database

Technical Details for CVE-2021-47815

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 resides in the registration key validation component of Nsauditor 3.2.3. When a user attempts to register the software, the application fails to properly validate the length of input provided in the 'Key' field before processing it. This oversight allows an attacker to supply an excessively long string that exceeds the allocated buffer size, resulting in memory corruption and subsequent application crash.

The attack requires local access to the system where Nsauditor is installed and user interaction to trigger the vulnerable code path through the registration interface. While this vulnerability does not enable code execution or data exfiltration, it effectively renders the network auditing tool unusable until restarted.

Root Cause

The root cause of this vulnerability 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 verify that user-supplied input fits within this boundary before copying data into memory. When 256 or more repeated characters are provided, the buffer overflows, corrupting adjacent memory structures and causing the application to crash.

Attack Vector

This is a local attack vector that requires physical or remote desktop access to the target system where Nsauditor is installed. The attacker must navigate to the registration dialog and paste a specially crafted string of 256 repeated characters into the 'Key' input field. Upon submission or processing of this input, the application crashes immediately.

The attack does not require elevated privileges or authentication beyond access to the application interface. While the vulnerability requires user interaction to trigger, it can be exploited reliably to deny service to network administrators depending on Nsauditor for their auditing workflows.

Technical details and proof-of-concept information are available through the Exploit-DB #49965 advisory and the VulnCheck Advisory for NSA Auditor.

Detection Methods for CVE-2021-47815

Indicators of Compromise

• Nsauditor application crashes or unexpected terminations, particularly during registration attempts
• Windows Error Reporting (WER) crash dumps indicating buffer overflow conditions in nsauditor.exe
• System event logs showing repeated application faults for the Nsauditor process

Detection Strategies

• Monitor for abnormal clipboard activity containing long repeated character strings being pasted into application input fields
• Implement endpoint detection rules to identify Nsauditor process crashes with memory access violation error codes
• Use application whitelisting and integrity monitoring to detect unauthorized access to the Nsauditor registration interface

Monitoring Recommendations

• Configure Windows Event Log monitoring to alert on Application Error events (Event ID 1000) specifically for nsauditor.exe
• Enable crash dump collection and analysis for the Nsauditor process to identify exploitation attempts
• Monitor user activity around the Nsauditor application, particularly access to registration or licensing dialogs

How to Mitigate CVE-2021-47815

Immediate Actions Required

• Verify the installed version of Nsauditor and determine if version 3.2.3 is deployed in your environment
• Contact Nsasoft through their official website to inquire about patched versions or security updates
• Restrict access to the Nsauditor application to authorized personnel only
• Consider implementing endpoint protection solutions that can detect and prevent buffer overflow exploitation attempts

Patch Information

No official vendor patch information has been published in the available CVE data. Organizations using Nsauditor 3.2.3 should contact Nsasoft directly to inquire about updated versions that address this vulnerability. Monitor the NSA Auditor Homepage for security updates and new releases.

Workarounds

• Restrict local access to systems running Nsauditor to trusted administrators only
• Use application control policies to prevent unauthorized users from accessing the registration interface
• Consider deploying alternative network auditing tools if a patched version is not available
• Implement process monitoring to automatically restart Nsauditor if it crashes unexpectedly

# Example: Windows Scheduled Task to monitor and restart Nsauditor
# Create a scheduled task that checks if nsauditor.exe is running
# and restarts it if not detected (mitigates DoS impact)
schtasks /create /tn "NsauditorMonitor" /tr "powershell -Command \"if (!(Get-Process nsauditor -ErrorAction SilentlyContinue)) { Start-Process 'C:\Program Files\Nsauditor\nsauditor.exe' }\"" /sc minute /mo 5