---
id: CVE-2026-125221
title: FFmpeg through 9.0.2 Uncontrolled Recursion in FLAC Parser score_header()
summary: >-
  FFmpeg through 9.0.2 contains an uncontrolled recursion vulnerability in
  score_header() in libavcodec/flac_parser.c that allows attackers to exhaust
  the thread stack via crafted FLAC input. Attackers can supply a FLAC stream
  packed with …
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-674
vendor: FFmpeg
product: FFmpeg
affected:
  - FFmpeg <= 9.0.2
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-09T20:59:31.174389Z'
published: '2026-11-09'
updated: '2026-11-09'
sourceUpdated: '2026-11-09T21:06:55.428Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-125221'
references:
  - url: 'https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/25569'
  - url: >-
      https://github.com/FFmpeg/FFmpeg/commit/972fe1ccd326538fe9a6b5d5094b7880b5443429
    label: Patch Commit
  - url: 'https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/flac_parser.c#L603'
  - url: 'https://github.com/FFmpeg/FFmpeg'
  - url: >-
      https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-uncontrolled-recursion-in-flac-parser-score-header
    label: >-
      VulnCheck Advisory: FFmpeg through 9.0.2 Uncontrolled Recursion in FLAC
      Parser score_header()
tags:
  - cve.org
ingestedAt: '2026-11-09T19:18:02.591Z'
---

## Overview

FFmpeg through 9.0.2 contains an uncontrolled recursion vulnerability in score_header() in libavcodec/flac_parser.c that allows attackers to exhaust the thread stack via crafted FLAC input. Attackers can supply a FLAC stream packed with many small valid-looking frame headers, forcing deep recursion that crashes the process during demuxing or parsing.

## Affected

- `FFmpeg <= 9.0.2`

## Remediation

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