FFmpeg through 9.0.2 WebP Decoder Information Disclosure via Short ALPH Chunk

Advisories

FFmpeg through 9.0.2 WebP Decoder Information Disclosure via Short ALPH Chunk

Severity: medium
Date: 11/9/2026
Affecting: FFmpeg <= 9.0.2
CVE: CVE-2026-125098
CWE: CWE-908 Use of Uninitialized Resource
CVSS: 4.8
CVSS V4 Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
References: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/25715
Patch Commit
https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/webp.c#L1257
https://github.com/FFmpeg/FFmpeg
Credit: Joshua Rogers (AISLE Research), Michael Niedermayer
Description: FFmpeg through 9.0.2 contains an information disclosure vulnerability in vp8_lossy_decode_alpha() in libavcodec/webp.c that leaves alpha plane memory uninitialized for short uncompressed ALPH chunks. Attackers can supply a crafted WebP image whose ALPH chunk is shorter than width * height to disclose stale pixel data from previously decoded frames.

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