FFmpeg through 9.0.2 GIF Encoder Heap Buffer Overflow via shrunk_buf Remap

Advisories

FFmpeg through 9.0.2 GIF Encoder Heap Buffer Overflow via shrunk_buf Remap

Severity: high
Date: 11/9/2026
Affecting: FFmpeg <= 9.0.2
CVE: CVE-2026-125250
CWE: CWE-122 Heap-based Buffer Overflow
CVSS: 8.5
CVSS V4 Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
References: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/25690
Patch Commit
https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/gif.c#L405
https://github.com/FFmpeg/FFmpeg
Credit: Joshua Rogers (AISLE Research), Michael Niedermayer
Description: FFmpeg through 9.0.2 contains a heap buffer overflow in the GIF encoder's gif_image_write_image() in libavcodec/gif.c because shrunk_buf is sized from the first frame's linesize. Attackers can supply PAL8 video whose frame linesize grows mid-stream, causing remap_frame_to_palette() to write past shrunk_buf and corrupt the heap during GIF transcoding.

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