CVE-2020-37155: Core FTP Lite Buffer Overflow Vulnerability

CVE-2020-37155 Overview

CVE-2020-37155 is a buffer overflow vulnerability affecting Core FTP Lite version 1.3. The vulnerability exists in the username input field and allows attackers to crash the application by supplying oversized input. Specifically, attackers can generate a 7000-byte payload of repeated 'A' characters to trigger an application crash without requiring additional interaction.

Critical Impact

This buffer overflow vulnerability enables denial of service attacks against Core FTP Lite 1.3, allowing attackers to crash the application through malformed username input, disrupting FTP operations.

Affected Products

• Core FTP Lite 1.3

Discovery Timeline

• 2026-02-07 - CVE CVE-2020-37155 published to NVD
• 2026-02-09 - Last updated in NVD database

Technical Details for CVE-2020-37155

Vulnerability Analysis

This vulnerability is classified as CWE-120 (Buffer Copy without Checking Size of Input), commonly known as a classic buffer overflow. The Core FTP Lite 1.3 application fails to properly validate the length of user-supplied input in the username field before copying it to a fixed-size buffer. When an attacker provides input exceeding the expected buffer size, the excess data overwrites adjacent memory locations, leading to application instability and crashes.

The local attack vector requires user interaction, meaning an attacker would need to convince a user to enter malicious input or load a configuration file containing the oversized payload. While this vulnerability primarily results in denial of service through application crashes, classic buffer overflows can potentially be leveraged for more severe exploitation in certain scenarios.

Root Cause

The root cause of this vulnerability is insufficient input validation in the username input field handling code. The application allocates a fixed-size buffer for storing username input but does not properly check the size of incoming data before copying it into this buffer. This lack of bounds checking allows attackers to provide input that exceeds the allocated buffer space, resulting in a buffer overflow condition.

Attack Vector

The attack vector for CVE-2020-37155 is local, requiring some form of user interaction. An attacker can exploit this vulnerability by:

1. Crafting a malicious payload consisting of approximately 7000 bytes of repeated characters (e.g., 'A' characters)
2. Inputting this payload into the username field of Core FTP Lite 1.3
3. The application attempts to process the oversized input, triggering the buffer overflow
4. The overflow causes memory corruption, leading to an immediate application crash

The attack does not require authentication or elevated privileges, but does require user interaction to input or load the malicious payload. Technical details and proof-of-concept information can be found in the Exploit-DB #48100 entry and the VulnCheck Advisory.

Detection Methods for CVE-2020-37155

Indicators of Compromise

• Unexpected Core FTP Lite application crashes or terminations
• Crash dump files showing buffer overflow patterns in the username handling routines
• Log entries indicating abnormally long username input attempts
• Application fault reports with memory access violations

Detection Strategies

• Monitor for Core FTP Lite process terminations that may indicate exploitation attempts
• Implement application crash monitoring to detect repeated denial of service attempts
• Deploy endpoint protection solutions capable of detecting buffer overflow exploitation patterns
• Review application logs for unusually long input strings in authentication fields

Monitoring Recommendations

• Enable detailed application logging for Core FTP Lite to capture authentication attempts
• Configure endpoint detection and response (EDR) solutions to monitor for memory corruption events
• Implement process monitoring to alert on unexpected Core FTP Lite crashes
• Consider deploying SentinelOne agents to detect and prevent buffer overflow exploitation attempts

How to Mitigate CVE-2020-37155

Immediate Actions Required

• Verify if Core FTP Lite 1.3 is deployed in your environment and inventory all affected installations
• Consider upgrading to a newer version of Core FTP if available, or evaluate alternative FTP clients
• Implement network segmentation to limit exposure of systems running vulnerable software
• Deploy endpoint protection solutions capable of detecting buffer overflow attacks

Patch Information

Consult the Core FTP Official Site for information on updated versions that may address this vulnerability. Organizations should check for available updates and apply them according to their patch management procedures. If no patch is available, consider implementing the workarounds described below.

Workarounds

• Restrict access to systems running Core FTP Lite 1.3 to trusted users only
• Implement application whitelisting to prevent unauthorized modifications to Core FTP Lite
• Consider using alternative FTP client software that is not affected by this vulnerability
• Deploy host-based intrusion prevention systems (HIPS) to detect and block exploitation attempts

# Configuration example - Restrict Core FTP Lite access
# Limit user permissions on the Core FTP Lite installation directory
# Windows example: Use NTFS permissions to restrict access
icacls "C:\Program Files\Core FTP Lite" /inheritance:r
icacls "C:\Program Files\Core FTP Lite" /grant:r Administrators:(OI)(CI)F
icacls "C:\Program Files\Core FTP Lite" /grant:r "Authenticated Users":(OI)(CI)RX