CVE-2026-125103

LOW 3.3

FFmpeg through 9.0.2 Uninitialized Heap Disclosure via MLZ Decompressor in ALS Decoder

CVSS Score

3.3

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-908
Vendor	ffmpeg
Product	ffmpeg
Published	Nov 9, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

Attack Vector

Local

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Affected Versions

FFmpeg / FFmpeg

0 ≤ 9.0.2

References

NVD ↗ CVE.org ↗ EPSS Data ↗

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

Credits

Joshua Rogers (AISLE Research) Michael Niedermayer