Integer Underflow in Bento4 MP4 Parser

Executive Summary

This vulnerability is an integer underflow issue in Bento4 version 1.6.0.0. It occurs in the functions AP4_AvccAtom::Create() and AP4_HvccAtom::Create() when processing MP4 files with avcC or hvcC atoms. If the declared size of such an atom is smaller than the atom header size, the payload-size calculation wraps to a large unsigned value. This leads to invalid buffer allocation and copy operations, causing the application to terminate and resulting in a denial of service.

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Detection Guidance

Detecting this vulnerability requires analyzing MP4 files for malformed avcC or hvcC atoms. Use tools like ffprobe or mediainfo to inspect atom structures. Check for atoms where the declared size is smaller than the atom header size (8 bytes).

Commands: ffprobe -show_frames -show_format -i input.mp4 | grep avcC or hvcC. Mediainfo --full input.mp4. Look for inconsistencies in atom sizes or parsing errors.

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Impact Analysis

This vulnerability can cause applications using Bento4 1.6.0.0 to crash when processing specially crafted MP4 files. The crash results in a denial of service, meaning the application becomes unavailable until restarted. Users may experience interrupted media processing or playback if they encounter files exploiting this issue.

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Compliance Impact

This vulnerability primarily causes denial-of-service conditions by crashing applications processing malformed MP4 files. It does not directly expose or leak data, so it may not directly violate GDPR or HIPAA data protection requirements. However, repeated crashes could disrupt services handling sensitive data, potentially impacting availability obligations under these regulations.

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Mitigation Strategies

Update Bento4 to the latest version where this issue is fixed. Avoid processing untrusted MP4 files until patched. Implement file validation before processing to reject malformed atoms.

Use sandboxing or isolated environments to limit impact if processing untrusted files. Monitor applications for crashes or denial of service during file parsing.

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