Integer Overflow in FFmpeg pcm_rechunk Bitstream Filter

Executive Summary

FFmpeg through version 9.0.2 has an integer overflow in the pcm_rechunk bitstream filter. Attackers can exploit this by providing a file with an extremely large channel count. When remuxed into formats like MXF, GXF, or DAUD, the sample_size calculation overflows, causing a division by zero and crashing the application.

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Detection Guidance

To detect this vulnerability, monitor FFmpeg processes for crashes when handling audio files with large channel counts. Use tools like ASAN or UBSAN to detect division by zero or integer overflows during FFmpeg operations. Check logs for crashes in FFmpeg versions up to 9.0.2 when processing MXF, GXF, or DAUD files.

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Impact Analysis

This vulnerability can cause FFmpeg to crash when processing malformed audio files. If exploited, it may lead to denial-of-service conditions, disrupting media processing tasks. Users relying on FFmpeg for audio/video conversion or editing could experience application failures.

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Mitigation Strategies

Immediately update FFmpeg to a patched version that includes the fix for the pcm_rechunk bitstream filter. Avoid processing untrusted audio files with FFmpeg until updated. Apply input validation to reject files with excessively large channel counts before processing.

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