---
id: CVE-2026-125203
title: >-
  FFmpeg before 8.1.3 and 9.x before 9.0.2 Heap Buffer Overflow in Cook
  Multichannel Decoder
summary: >-
  FFmpeg before 8.1.3 and 9.x before 9.0.2 contains a heap buffer overflow
  vulnerability in the Cook multichannel decoder in libavcodec/cook.c that fails
  to verify subpacket channel masks are disjoint. Attackers can supply a crafted
  RealMe…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H'
cvssSource: cna
cwe:
  - CWE-787
vendor: FFmpeg
product: FFmpeg
affected:
  - FFmpeg < 8.1.3
  - FFmpeg >= 9.0 < 9.0.2
published: '2026-11-09'
updated: '2026-11-09'
sourceUpdated: '2026-11-09T19:11:22.136Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-125203'
references:
  - url: 'https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24485'
  - url: >-
      https://github.com/FFmpeg/FFmpeg/commit/3e09f5e24eb277a6d011745ff03e602f61c5c171
    label: Patch Commit
  - url: 'https://github.com/FFmpeg/FFmpeg/blob/n9.0.1/libavcodec/cook.c#L1294'
  - url: 'https://github.com/FFmpeg/FFmpeg'
  - url: >-
      https://www.vulncheck.com/advisories/ffmpeg-before-8.1.3-and-9-x-before-9.0.2-heap-buffer-overflow-in-cook-multichannel-decoder
    label: >-
      VulnCheck Advisory: FFmpeg before 8.1.3 and 9.x before 9.0.2 Heap Buffer
      Overflow in Cook Multichannel Decoder
tags:
  - cve.org
ingestedAt: '2026-11-09T19:18:02.598Z'
---

## Overview

FFmpeg before 8.1.3 and 9.x before 9.0.2 contains a heap buffer overflow vulnerability in the Cook multichannel decoder in libavcodec/cook.c that fails to verify subpacket channel masks are disjoint. Attackers can supply a crafted RealMedia Cook stream with overlapping subpacket masks, causing cook_decode_frame() to write decoded samples beyond allocated output planes in any application decoding the file.

## Affected

- `FFmpeg < 8.1.3`
- `FFmpeg >= 9.0 < 9.0.2`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.