CVE-2021-47895: Nsauditor 3.2.2.0 DoS Vulnerability

CVE-2021-47895 Overview

CVE-2021-47895 is a denial of service vulnerability affecting Nsauditor version 3.2.2.0. The vulnerability allows attackers to crash the application by overwriting the Event Description field with an excessively large buffer. Specifically, an attacker can generate a 10,000-character buffer consisting of 'U' characters and paste it into the Event Description field, triggering an application crash and resulting in a denial of service condition.

Critical Impact

Attackers can cause the Nsauditor application to crash by exploiting improper resource allocation in the Event Description field, leading to service disruption.

Affected Products

• Nsauditor 3.2.2.0

Discovery Timeline

• 2026-01-23 - CVE CVE-2021-47895 published to NVD
• 2026-01-26 - Last updated in NVD database

Technical Details for CVE-2021-47895

Vulnerability Analysis

This vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling). The core issue stems from the application's failure to properly validate or limit the size of input data in the Event Description field. When a user or attacker inputs an abnormally large string (approximately 10,000 characters), the application fails to handle this excessive input gracefully, resulting in resource exhaustion and subsequent application crash.

The local attack vector requires user interaction, as the attacker must either have local access to the application or convince a legitimate user to paste the malicious buffer into the vulnerable field. Despite requiring user interaction, the vulnerability poses a significant availability risk to organizations relying on Nsauditor for network security auditing tasks.

Root Cause

The root cause of this vulnerability is the lack of proper input validation and resource allocation limits within the Event Description field handler. The application does not implement adequate bounds checking or memory management controls when processing user-supplied input, allowing an oversized buffer to overwhelm the application's memory allocation capabilities and cause a crash.

Attack Vector

The attack requires local access to the Nsauditor application. An attacker must create a specially crafted buffer containing approximately 10,000 'U' characters and paste this buffer into the Event Description field. Upon processing this oversized input, the application fails to allocate resources properly, leading to an unhandled exception and application termination.

The vulnerability mechanism involves pasting an oversized character buffer (10,000 'U' characters) into the Event Description field. When the application attempts to process this input without proper bounds checking, it exhausts available resources and crashes. Technical details and a proof-of-concept are available in the Exploit-DB #49568 entry.

Detection Methods for CVE-2021-47895

Indicators of Compromise

• Unexpected Nsauditor application crashes or terminations
• Event logs showing application failures related to memory allocation or unhandled exceptions
• Presence of unusually large text strings in Event Description fields or related configuration files
• User reports of application instability when working with event descriptions

Detection Strategies

• Monitor application event logs for crash events or memory-related errors in Nsauditor
• Implement endpoint detection rules to identify patterns of repeated application crashes
• Use file integrity monitoring to detect modifications to Nsauditor configuration files containing suspicious large text entries
• Deploy SentinelOne agents to detect and alert on application crash patterns indicative of DoS exploitation

Monitoring Recommendations

• Enable detailed logging for Nsauditor application events and crashes
• Configure alerting thresholds for repeated application terminations within short time periods
• Monitor system resource utilization (memory, CPU) on hosts running Nsauditor for anomalous spikes
• Implement user activity monitoring to detect suspicious paste operations or input patterns

How to Mitigate CVE-2021-47895

Immediate Actions Required

• Review and restrict access to systems running Nsauditor 3.2.2.0 to trusted users only
• Implement application whitelisting to prevent unauthorized modifications to Nsauditor
• Monitor for application crashes and investigate any suspicious activity
• Consider temporarily disabling or restricting access to the Event Description functionality if possible

Patch Information

Check with the vendor (NSA Auditor Tool) for updated versions that address this vulnerability. Review the VulnCheck Advisory on NSA Auditor for the latest remediation guidance and patch availability information.

Workarounds

• Restrict physical and remote access to systems running the vulnerable Nsauditor version
• Implement strict access controls limiting who can interact with the Event Description field
• Train users to avoid pasting untrusted or excessively large content into application fields
• Consider using alternative network auditing tools until a patch is available

# Configuration example
# Restrict user access to Nsauditor installation directory (Windows)
# Run in an elevated PowerShell session
icacls "C:\Program Files\Nsauditor" /inheritance:r /grant:r "BUILTIN\Administrators:(OI)(CI)F" /grant:r "NT AUTHORITY\SYSTEM:(OI)(CI)F"