CVE-2018-25323 Overview
CVE-2018-25323 is a Structured Exception Handler (SEH) buffer overflow vulnerability in Allok AVI DivX MPEG to DVD Converter version 2.6.1217. The flaw resides in the License Name input field of the application's registration dialog. A local attacker can paste a specially crafted payload containing shellcode and SEH chain overwrite values into the field to execute arbitrary code in the context of the running user. The vulnerability is classified under CWE-120: Buffer Copy without Checking Size of Input.
Critical Impact
Local attackers can achieve arbitrary code execution by supplying a crafted string to the License Name field, bypassing default SEH-based exception protections.
Affected Products
- Allok AVI DivX MPEG to DVD Converter 2.6.1217
- Earlier vulnerable builds in the Allok AVI DivX MPEG to DVD Converter 2.x line
- Windows installations bundling the vulnerable converter binary
Discovery Timeline
- 2026-05-17 - CVE-2018-25323 published to NVD
- 2026-05-18 - Last updated in NVD database
Technical Details for CVE-2018-25323
Vulnerability Analysis
The vulnerability is a classic stack-based buffer overflow that overwrites the Structured Exception Handler (SEH) chain on Windows. Allok AVI DivX MPEG to DVD Converter 2.6.1217 fails to validate the length of user input supplied to the License Name field. When an oversized string is pasted into this field, the application copies the data onto the stack without bounds checking. The overflow reaches the SEH record, allowing an attacker to overwrite both the next SEH pointer and the SEH handler address.
When the application later triggers an exception, the corrupted handler diverts execution to attacker-controlled memory. This grants arbitrary code execution with the privileges of the user running the converter.
Root Cause
The root cause is missing input length validation on the License Name registration field. The application uses an unsafe string copy routine to move the user-supplied data into a fixed-size stack buffer. Because the binary was not compiled with SafeSEH or SEHOP protections enforced on all modules, the overwritten exception handler is dispatched without integrity checks.
Attack Vector
The attack requires local access to the host running the vulnerable application. An attacker prepares a text file containing a buffer of padding bytes, an SEH chain overwrite, and shellcode. The attacker then opens the converter, navigates to the registration dialog, and pastes the contents into the License Name field. Triggering the resulting exception transfers control to the shellcode. Public exploitation details are available in Exploit-DB entry 44363 and the VulnCheck advisory for Allok AVI.
No verified code example is reproduced here. Refer to the public Exploit-DB submission for the full proof-of-concept structure.
Detection Methods for CVE-2018-25323
Indicators of Compromise
- Presence of the Allok AVI DivX MPEG to DVD Converter 2.6.1217 binary on endpoints, particularly on shared or kiosk systems.
- Unexpected child processes spawned by the converter executable, such as cmd.exe, powershell.exe, or other interpreters.
- Crash dumps or Windows Error Reporting entries referencing access violations inside the converter process with a corrupted SEH chain.
Detection Strategies
- Hunt for process creation events where the Allok converter is the parent of shells, scripting hosts, or network utilities.
- Inspect endpoint telemetry for memory protection violations and exception handler overwrites originating in the converter's process space.
- Correlate user paste activity into the registration dialog with subsequent abnormal process behavior on the same host.
Monitoring Recommendations
- Enable Windows Event Tracing and EDR process lineage logging for any host that retains legacy media conversion tools.
- Alert on execution of the Allok converter from non-standard paths or by service accounts that should not run interactive media software.
- Monitor for new instances of the vulnerable binary being introduced via software deployment systems or user downloads.
How to Mitigate CVE-2018-25323
Immediate Actions Required
- Remove Allok AVI DivX MPEG to DVD Converter 2.6.1217 from all managed endpoints, as the product is end-of-life and unsupported.
- Block execution of the converter binary using application control policies such as Windows Defender Application Control or AppLocker.
- Restrict local user privileges to limit the impact of code execution if the application cannot be removed immediately.
Patch Information
No vendor patch is available for CVE-2018-25323. Allok Soft Inc. has not published a fixed version of the AVI DivX MPEG to DVD Converter addressing this SEH buffer overflow. Organizations should migrate to a maintained media conversion product. See the VulnCheck advisory for advisory status.
Workarounds
- Uninstall the affected application entirely where business needs do not require it.
- Enforce Data Execution Prevention (DEP) and system-wide SEHOP via Windows Exploit Protection settings to raise the cost of SEH-based exploitation.
- Apply application allowlisting to prevent untrusted users from launching the vulnerable binary on shared workstations.
# Configuration example: enable system-wide SEHOP and DEP on Windows via PowerShell
Set-ProcessMitigation -System -Enable SEHOP,DEP
Set-ProcessMitigation -Name AllokAVItoDVD.exe -Enable SEHOP,DEP,BottomUp,ForceRelocateImages
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
