CVE-2026-125103

CVSS 4.8 (medium) · published 2026-11-09

FFmpeg through 9.0.2 contains an information disclosure vulnerability in ff_mlz_decompression() in libavcodec/mlz.c, which accepts string codes beyond the dictionary's next free code. Attackers can supply a crafted MPEG-4 ALS file with malformed initial or out-of-range codes to copy uninitialized heap bytes into decoded audio output.

Weakness: CWE-908

Source: NVD CVE-2026-125103

References

• https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/25703
• https://github.com/FFmpeg/FFmpeg
• https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/mlz.c#L161
• https://github.com/FFmpeg/FFmpeg/commit/db98784a72600a94f7ebd5f016a37e01a505c27b
• https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-uninitialized-heap-disclosure-via-mlz-decompressor-in-als-decoder

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