CVE-2018-25302: Allok AVI Converter Buffer Overflow Flaw

CVE-2018-25302 Overview

CVE-2018-25302 is a structured exception handling (SEH) based buffer overflow vulnerability in Allok AVI to DVD SVCD VCD Converter version 4.0.1217. This vulnerability allows local attackers to execute arbitrary code by supplying a malicious string in the License Name field during the software registration process.

Critical Impact

Successful exploitation enables local attackers to execute arbitrary code with the privileges of the application, potentially leading to complete system compromise.

Affected Products

• Allok AVI to DVD SVCD VCD Converter version 4.0.1217

Discovery Timeline

• 2026-04-29 - CVE CVE-2018-25302 published to NVD
• 2026-04-29 - Last updated in NVD database

Technical Details for CVE-2018-25302

Vulnerability Analysis

This vulnerability is classified as CWE-120 (Buffer Copy without Checking Size of Input), commonly known as a classic buffer overflow. The application fails to properly validate the length of user-supplied input in the License Name field of the registration dialog. When an attacker supplies an oversized input string, it overflows the allocated buffer and overwrites critical memory structures, including the Structured Exception Handler (SEH) chain.

The exploitation requires local access and user interaction—specifically, the victim must paste the malicious payload into the License Name field and click the Register button. Despite the local access requirement, the impact is severe as successful exploitation results in arbitrary code execution.

Root Cause

The root cause is improper input validation in the license registration functionality. The application allocates a fixed-size buffer for the License Name field but does not enforce length restrictions when copying user input into this buffer. This allows an attacker to supply a string that exceeds the buffer's capacity, causing a stack-based buffer overflow that corrupts adjacent memory, including SEH pointers.

Attack Vector

The attack requires local access to the target system with the Allok AVI to DVD SVCD VCD Converter software installed. An attacker crafts a malicious payload containing:

1. Junk data - Initial padding to fill the buffer up to the SEH chain
2. NSEH bypass - Overwrites the Next SEH pointer with a short jump instruction
3. SEH handler address - Points to a POP POP RET gadget within the application or loaded modules
4. Shellcode - The actual malicious payload to be executed

When the crafted string is pasted into the License Name field and the Register button is clicked, an exception is triggered. The corrupted SEH handler redirects execution flow to the attacker's shellcode, resulting in arbitrary code execution.

The attack exploits the SEH mechanism commonly used in Windows applications for exception handling, making it a classic Windows-specific exploitation technique.

Detection Methods for CVE-2018-25302

Indicators of Compromise

• Unusual crashes or exceptions in Allok AVI to DVD SVCD VCD Converter processes
• Presence of suspicious strings or binary data in application log files related to license registration
• Unexpected child processes spawned by the Allok converter application

Detection Strategies

• Monitor for process crashes associated with Allok AVI to DVD SVCD VCD Converter that may indicate exploitation attempts
• Implement endpoint detection rules to identify SEH-based buffer overflow patterns
• Use application whitelisting to prevent unauthorized code execution from exploitation

Monitoring Recommendations

• Deploy endpoint detection and response (EDR) solutions capable of detecting memory corruption exploitation techniques
• Monitor for anomalous process behavior from legacy media conversion applications
• Consider removing or isolating systems running vulnerable versions of this software

How to Mitigate CVE-2018-25302

Immediate Actions Required

• Uninstall Allok AVI to DVD SVCD VCD Converter version 4.0.1217 if not required for business operations
• Restrict local access to systems with this vulnerable software installed
• Implement application control policies to prevent unauthorized registration attempts
• Consider migrating to alternative, actively maintained video conversion software

Patch Information

No vendor patch is currently available for this vulnerability. The software appears to be legacy/abandoned software from AllokSoft. Users should consider this application end-of-life and migrate to alternative solutions.

For additional technical details, refer to the VulnCheck Security Advisory and Exploit-DB #44549.

Workarounds

• Remove the vulnerable application from production systems
• If the application must remain installed, restrict access to trusted users only and disable the registration functionality
• Implement Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) at the system level to make exploitation more difficult
• Use application sandboxing to limit the impact of potential exploitation