CVE-2020-37119: Nsauditor Buffer Overflow Vulnerability

CVE-2020-37119 Overview

CVE-2020-37119 is a stack-based buffer overflow vulnerability affecting Nsauditor versions 3.0.28 and 3.2.1.0. The vulnerability exists in the DNS Lookup tool component and allows attackers to execute arbitrary code by overwriting memory. Attackers can craft a malicious DNS query payload to trigger a three-byte overwrite, bypass ASLR, and execute shellcode through a carefully constructed exploit.

Critical Impact

This buffer overflow vulnerability enables arbitrary code execution through memory corruption, potentially allowing attackers to gain complete control of affected systems running vulnerable Nsauditor versions.

Affected Products

• Nsauditor version 3.0.28
• Nsauditor version 3.2.1.0

Discovery Timeline

• 2026-02-05 - CVE CVE-2020-37119 published to NVD
• 2026-02-05 - Last updated in NVD database

Technical Details for CVE-2020-37119

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), which occurs when a program writes more data to a buffer on the stack than it can hold. In Nsauditor's DNS Lookup tool, insufficient bounds checking on user-supplied DNS query input allows an attacker to overflow a fixed-size buffer, corrupting adjacent memory on the stack.

The local attack vector requires user interaction, meaning an attacker must convince a user to perform a DNS lookup using a maliciously crafted payload. Once triggered, the overflow enables a three-byte memory overwrite that can be leveraged to bypass Address Space Layout Randomization (ASLR) protections and redirect program execution to attacker-controlled shellcode.

Root Cause

The root cause of this vulnerability lies in improper input validation within the DNS Lookup tool's query processing logic. The application fails to properly validate the length of DNS query input before copying it into a fixed-size stack buffer. This missing boundary check allows oversized input to overflow the buffer and corrupt critical stack data, including return addresses and saved frame pointers.

Attack Vector

The attack requires local access to the vulnerable Nsauditor application and user interaction to trigger the DNS Lookup functionality with a malicious payload. An attacker would:

1. Craft a specially formatted DNS query payload exceeding the expected buffer size
2. Include carefully positioned data to achieve the three-byte overwrite
3. Leverage the overwrite to bypass ASLR protections
4. Redirect execution flow to attacker-supplied shellcode

The vulnerability mechanism involves precise memory manipulation through the buffer overflow. Technical details and proof-of-concept information are available through the Exploit-DB #48350 entry and the VulnCheck Advisory on Buffer Overflow.

Detection Methods for CVE-2020-37119

Indicators of Compromise

• Unexpected crashes or abnormal termination of the Nsauditor application, particularly during DNS Lookup operations
• Memory access violation errors or exception handling events in system logs
• Unusual process behavior following DNS query execution, such as spawning child processes or network connections
• Evidence of shellcode execution patterns in memory forensics

Detection Strategies

• Monitor for anomalous DNS query lengths that significantly exceed normal operational parameters
• Implement endpoint detection rules for stack buffer overflow patterns targeting Nsauditor processes
• Use application whitelisting to detect unauthorized code execution originating from Nsauditor
• Deploy behavioral analysis to identify post-exploitation activities following Nsauditor crashes

Monitoring Recommendations

• Enable detailed application logging for Nsauditor operations
• Configure endpoint detection and response (EDR) solutions to alert on memory corruption indicators
• Monitor system event logs for application fault reports involving nsauditor.exe
• Implement network monitoring to detect potential command-and-control communications following exploitation

How to Mitigate CVE-2020-37119

Immediate Actions Required

• Restrict access to Nsauditor application to only authorized personnel who require the functionality
• Avoid using the DNS Lookup tool with untrusted or suspicious input until a patch is available
• Consider temporarily disabling or removing Nsauditor if the functionality is not critical
• Implement network segmentation to limit the impact of potential compromise

Patch Information

Users should check the NSA Auditor Overview vendor website for updated versions that address this vulnerability. It is recommended to upgrade to the latest available version once a security patch has been released.

Workarounds

• Disable or restrict access to the DNS Lookup tool functionality within Nsauditor
• Use alternative DNS lookup utilities that do not contain this vulnerability
• Implement application-level firewall rules to monitor and control Nsauditor's network activity
• Run Nsauditor in a sandboxed or virtualized environment to contain potential exploitation