This vulnerability is a stack-based buffer overflow (CWE-121) in the scanning engine of Gen Digital's Avast Antivirus and related products triggered by malformed Office Open XML files. It can cause denial-of-service by crashing the antivirus process. The affected products include Avast Antivirus, AVG Antivirus, Norton Antivirus, Avast One, and Avast Business Antivirus across Windows, macOS, and Linux. The vulnerability is present in virus definition builds before VPS 25020100. The shared virus definition update stream delivers the vulnerable scanning logic, and updating to VPS 25020100 or later mitigates the issue regardless of the specific product using the engine.

Successful exploitation results in denial-of-service of the antivirus process, potentially disrupting malware scanning and protection. There is no indication of confidentiality or integrity impact. The vulnerability requires local access to scan a crafted Office Open XML file and user interaction to trigger the scan. The CVSS v3.1 base score is 5.5 (medium severity), reflecting local attack vector, low complexity, no privileges required, user interaction needed, and impact limited to availability.

Updating virus definitions to build VPS 25020100 or later fully mitigates this vulnerability. Since the scanning logic is delivered via the virus definition update stream, ensuring that antivirus products receive and apply this update removes the vulnerability. There is no separate patch or fix required beyond applying the updated virus definitions. Users should verify their antivirus products have virus definitions at or above VPS 25020100.