CVE-2020-37010: BearShare Lite Buffer Overflow Flaw

CVE-2020-37010 Overview

CVE-2020-37010 is a buffer overflow vulnerability discovered in BearShare Lite version 5.2.5. The vulnerability exists in the Advanced Search functionality, specifically within the keywords input field. By crafting a specially designed malicious payload, attackers can overwrite the EIP (Extended Instruction Pointer) register and execute arbitrary shellcode on the target system.

This classic buffer overflow attack requires user interaction, where the victim must paste malicious content into the search keywords field. Once triggered, the attacker can gain code execution with the privileges of the current user running the BearShare Lite application.

Critical Impact

Successful exploitation allows attackers to execute arbitrary code on the victim's system by overwriting the EIP register, potentially leading to full system compromise.

Affected Products

• BearShare Lite 5.2.5

Discovery Timeline

• 2026-01-29 - CVE-2020-37010 published to NVD
• 2026-01-29 - Last updated in NVD database

Technical Details for CVE-2020-37010

Vulnerability Analysis

The vulnerability is classified under CWE-120 (Buffer Copy without Checking Size of Input), a classic memory corruption issue where the application fails to properly validate the length of user-supplied input before copying it into a fixed-size buffer.

When a user enters search keywords in the Advanced Search feature of BearShare Lite, the application allocates a buffer of predetermined size to store this input. The vulnerability arises because the application does not perform adequate bounds checking on the input data. When an attacker supplies input exceeding the buffer's allocated size, the excess data overwrites adjacent memory locations on the stack.

The attack requires local access to the system and user interaction to trigger. The victim must actively paste the malicious payload into the search keywords field, making this a client-side attack that could be delivered through social engineering tactics.

Root Cause

The root cause of CVE-2020-37010 is improper input validation in the Advanced Search functionality. The application fails to verify that user-supplied input does not exceed the allocated buffer size before performing the copy operation. This allows attackers to overflow the stack buffer, overwriting the saved return address (EIP) with a controlled value that redirects execution flow to attacker-supplied shellcode.

Attack Vector

The attack vector is local, requiring the attacker to either have direct access to the system or convince the victim to paste malicious content into the application. The exploitation process typically involves:

1. Generating a payload that exceeds the buffer size allocated for search keywords
2. Including padding to reach the EIP offset
3. Overwriting the EIP with an address pointing to shellcode or a return-oriented programming (ROP) gadget
4. Placing shellcode in a predictable memory location

The attacker crafts a payload containing a specific number of bytes to fill the buffer, followed by an address that overwrites the saved return pointer. When the vulnerable function returns, execution jumps to the attacker-controlled address, executing the embedded shellcode. A proof-of-concept exploit is documented in Exploit-DB #48839.

Detection Methods for CVE-2020-37010

Indicators of Compromise

• Presence of BearShare Lite version 5.2.5 installed on endpoints
• Unusual process behavior or child processes spawned from bearshare.exe
• Memory corruption artifacts or crash dumps indicating stack buffer overflow conditions
• Unexpected network connections originating from the BearShare Lite process

Detection Strategies

• Monitor for abnormal memory access patterns in BearShare Lite processes
• Deploy endpoint detection rules to identify buffer overflow exploitation attempts against legacy P2P applications
• Implement application whitelisting to prevent execution of unauthorized code from BearShare Lite context
• Enable DEP (Data Execution Prevention) and ASLR (Address Space Layout Randomization) on systems where BearShare Lite is installed

Monitoring Recommendations

• Audit systems for installations of BearShare Lite 5.2.5 and flag for removal or upgrade
• Configure SIEM rules to alert on crashes or exceptions in legacy file-sharing applications
• Monitor clipboard activity for potential exploitation payloads being pasted into vulnerable applications

How to Mitigate CVE-2020-37010

Immediate Actions Required

• Uninstall BearShare Lite 5.2.5 from all systems as this is legacy software with known vulnerabilities
• If removal is not immediately possible, restrict application usage through Group Policy or application control
• Enable exploit mitigations such as DEP and ASLR at the operating system level
• Educate users about the risks of pasting untrusted content into applications

Patch Information

No official vendor patch is available for this vulnerability. BearShare Lite is legacy software that is no longer actively maintained. The recommended remediation is to completely remove the application from affected systems. For more information, refer to the VulnCheck Advisory or the BearShare Official Website.

Workarounds

• Remove BearShare Lite entirely and migrate to actively supported file-sharing alternatives
• If removal is not feasible, run the application in an isolated virtual machine or sandboxed environment
• Block clipboard operations to the BearShare Lite application using endpoint security tools
• Implement application control policies to prevent BearShare Lite from executing

# Example: Remove BearShare Lite from Windows systems via command line
# Uninstall using Windows Installer (if installed via MSI)
wmic product where "name like 'BearShare%%'" call uninstall /nointeractive

# Alternative: Block execution using Group Policy AppLocker
# Create a deny rule for bearshare.exe in the AppLocker configuration