Vulnerability in Ffmpeg
CVE-2026-125221
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.
Published .
CVSS v3 metric
CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- code.ffmpeg.org/FFmpeg/FFmpeg/pulls/25569 (issue-tracking)
- github.com/FFmpeg/FFmpeg (product)
- github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/flac_parser.c (technical-description)
- Patch Commit (patch)
- VulnCheck Advisory: FFmpeg through 9.0.2 Uncontrolled Recursion in FLAC Parser score_header() (third-party-advisory)
Frequently asked questions
- What is CVE-2026-125221?
- CVE-2026-125221 is a medium-severity vulnerability in Ffmpeg, classified under Uncontrolled Recursion. CVSS score: 5.5/10. Published 2026-11-09.
- How severe is CVE-2026-125221?
- Medium severity. CVSS v3 base score is 5.5 out of 10.