CVE-2019-25666: SpotAuditor Base64 DoS Vulnerability

CVE-2019-25666 Overview

CVE-2019-25666 is a local buffer overflow vulnerability affecting SpotAuditor version 3.6.7, specifically within the Base64 Password Decoder component. This vulnerability allows local attackers to crash the application by supplying an oversized Base64 string through the decoder interface, resulting in a denial of service condition.

The vulnerability is classified as CWE-787 (Out-of-Bounds Write), indicating that the application writes data past the end or before the beginning of the intended buffer when processing Base64-encoded input.

Critical Impact

Local attackers can cause application crashes and denial of service by exploiting the buffer overflow in SpotAuditor's Base64 Password Decoder component.

Affected Products

• SpotAuditor 3.6.7
• Base64 Password Decoder component within SpotAuditor

Discovery Timeline

• 2026-04-05 - CVE-2019-25666 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2019-25666

Vulnerability Analysis

This vulnerability exists in the Base64 Password Decoder functionality of SpotAuditor, a password auditing tool. The application fails to properly validate the length of user-supplied Base64-encoded strings before processing them. When an attacker provides an excessively long Base64 string to the decoder interface, the application attempts to write the decoded data into a fixed-size buffer without adequate bounds checking.

The out-of-bounds write condition (CWE-787) occurs because the decoder does not enforce a maximum input length, allowing attackers to overflow the destination buffer. This results in memory corruption that causes the application to crash, creating a denial of service condition.

While the vulnerability requires local access to exploit, it does not require any user privileges or interaction, making it relatively straightforward to trigger once an attacker has access to the system running SpotAuditor.

Root Cause

The root cause of this vulnerability is improper input validation in the Base64 Password Decoder component. The decoder fails to validate or restrict the size of incoming Base64 strings before attempting to decode and store them in memory. Without proper boundary checks, oversized input leads to a buffer overflow condition, corrupting adjacent memory and causing application instability.

Attack Vector

The attack vector is local, requiring an attacker to have access to a system where SpotAuditor is installed. The attacker can exploit this vulnerability by:

1. Accessing the SpotAuditor application's Base64 Password Decoder interface
2. Providing a specially crafted, oversized Base64 string as input
3. Triggering the buffer overflow when the application attempts to decode the malicious input
4. Causing the application to crash due to memory corruption

The vulnerability allows attackers to disrupt availability of the SpotAuditor application. Additional technical details can be found in the Exploit-DB #46313 advisory and the VulnCheck Denial of Service Advisory.

Detection Methods for CVE-2019-25666

Indicators of Compromise

• Unexpected SpotAuditor application crashes or termination
• Application error logs showing memory access violations or buffer overflow exceptions
• Unusually large Base64 strings present in application logs or input queues
• Repeated attempts to access the Base64 Password Decoder feature

Detection Strategies

• Monitor SpotAuditor processes for unexpected crashes or memory exceptions
• Implement application crash monitoring to detect denial of service attempts
• Review system event logs for application fault entries related to SpotAuditor
• Deploy endpoint detection solutions to identify suspicious input patterns to the application

Monitoring Recommendations

• Enable verbose logging for SpotAuditor to capture input processing events
• Configure crash dump collection for post-incident forensic analysis
• Monitor for repeated application restarts that may indicate ongoing exploitation attempts
• Implement real-time alerting for SpotAuditor process terminations

How to Mitigate CVE-2019-25666

Immediate Actions Required

• Restrict access to SpotAuditor to only authorized personnel on secured systems
• Consider disabling or limiting access to the Base64 Password Decoder feature if not essential
• Monitor systems running SpotAuditor for signs of exploitation
• Review access controls on systems where SpotAuditor is installed

Patch Information

Users should check with the vendor for updated versions of SpotAuditor that address this buffer overflow vulnerability. Visit the NSA Auditor Order Page for product information and potential updates.

Organizations should prioritize upgrading to patched versions when available, or consider alternative password auditing tools if no fix is released for version 3.6.7.

Workarounds

• Limit access to the SpotAuditor application to trusted users only
• Implement input validation at the network or application level to reject oversized Base64 strings before they reach SpotAuditor
• Consider running SpotAuditor in an isolated environment to minimize the impact of potential crashes
• Use application whitelisting to control which users can execute SpotAuditor

# Restrict SpotAuditor execution to specific users (Windows)
# Use NTFS permissions to limit application access
icacls "C:\Program Files\SpotAuditor" /inheritance:r
icacls "C:\Program Files\SpotAuditor" /grant:r "DOMAIN\SecurityTeam:(OI)(CI)F"
icacls "C:\Program Files\SpotAuditor" /grant:r "BUILTIN\Administrators:(OI)(CI)F"