CVE-2020-37183: Allok RM RMVB Converter Buffer Overflow

CVE-2020-37183 Overview

CVE-2020-37183 is a stack overflow vulnerability affecting Allok RM RMVB to AVI MPEG DVD Converter version 3.6.1217. This vulnerability allows attackers to execute arbitrary code by overwriting Structured Exception Handler (SEH) registers through a crafted malicious payload in the License Name input field. The vulnerability is classified as CWE-121 (Stack-based Buffer Overflow).

Critical Impact

Successful exploitation allows attackers to execute arbitrary system commands, potentially leading to complete system compromise through SEH overwrite techniques.

Affected Products

• Allok RM RMVB to AVI MPEG DVD Converter version 3.6.1217

Discovery Timeline

• 2026-02-11 - CVE CVE-2020-37183 published to NVD
• 2026-02-12 - Last updated in NVD database

Technical Details for CVE-2020-37183

Vulnerability Analysis

This vulnerability exists in the license registration functionality of Allok RM RMVB to AVI MPEG DVD Converter. The application fails to properly validate the length of user-supplied input in the License Name field before copying it to a fixed-size stack buffer. When an attacker provides an excessively long string in this field, it overflows the allocated buffer and corrupts adjacent memory, including the Structured Exception Handler (SEH) chain.

The attack requires local access and user interaction, as the victim must open or interact with a malicious license file or input the crafted payload directly into the application's registration dialog. Once the buffer overflow occurs, the attacker can redirect program execution by overwriting the SEH handler address, ultimately gaining code execution in the context of the vulnerable application.

Root Cause

The root cause is improper bounds checking on the License Name input field. The application allocates a fixed-size buffer on the stack but does not validate that user input conforms to this size limit before performing a copy operation. This classic stack-based buffer overflow condition (CWE-121) allows attackers to write beyond the intended buffer boundaries and corrupt critical control structures on the stack.

Attack Vector

The attack vector is local, requiring an attacker to either have direct access to the system or convince a user to input a malicious string into the License Name field. The exploitation technique leverages SEH overwrite, a well-documented method for bypassing stack protection mechanisms on Windows systems. By carefully crafting the overflow payload, attackers can overwrite the SEH handler pointer and trigger an exception to redirect execution flow to their shellcode, enabling arbitrary command execution such as launching calc.exe as demonstrated in public exploits.

The vulnerability mechanism involves overflowing the stack buffer in the License Name input field, overwriting the SEH chain with attacker-controlled values, and triggering an exception to execute malicious code. For technical exploitation details, see the Exploit-DB #47910 entry and the VulnCheck Security Advisory.

Detection Methods for CVE-2020-37183

Indicators of Compromise

• Presence of Allok RM RMVB to AVI MPEG DVD Converter version 3.6.1217 installed on endpoints
• Unusual process spawning from the converter application (e.g., cmd.exe, calc.exe, or other unexpected child processes)
• Application crashes or exception errors during license registration attempts
• Anomalous memory access patterns or SEH chain corruption in process memory dumps

Detection Strategies

• Deploy endpoint detection rules to monitor for buffer overflow exploitation attempts targeting the Allok converter application
• Implement application allowlisting to prevent execution of unauthorized child processes spawned by the converter
• Use behavioral analysis to detect SEH overwrite patterns and shellcode execution attempts
• Monitor for crash dumps or Windows Error Reporting events associated with the vulnerable application

Monitoring Recommendations

• Enable detailed logging for application execution and child process creation on systems where the vulnerable software is installed
• Configure SIEM rules to correlate converter application execution with suspicious process trees
• Implement file integrity monitoring for the application directory to detect unauthorized modifications
• Review endpoint telemetry for exploitation indicators such as unexpected exception handling behavior

How to Mitigate CVE-2020-37183

Immediate Actions Required

• Uninstall Allok RM RMVB to AVI MPEG DVD Converter version 3.6.1217 from all affected systems immediately
• Consider migrating to alternative video conversion software that is actively maintained with security updates
• Restrict execution of the vulnerable application using application control policies
• Educate users not to enter untrusted license information into the application

Patch Information

No official vendor patch is currently available for this vulnerability. The vendor website at Alloksoft Homepage should be monitored for any security updates. Given the lack of active vendor support, the recommended remediation is to discontinue use of this software and transition to a supported alternative.

Workarounds

• Remove or quarantine the vulnerable application from production systems until a patch becomes available
• Implement Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) at the OS level to make exploitation more difficult
• Use application sandboxing solutions to isolate the converter application from critical system resources
• Block execution of the vulnerable application via Windows AppLocker or similar endpoint security controls

# Example AppLocker rule to block the vulnerable application
# Add to your AppLocker policy XML or configure via Group Policy
# Block path: C:\Program Files*\Allok*\*.exe