What is CVE-2026-125246?

CVE-2026-125246 is a medium-severity vulnerability in Ffmpeg, classified under Reachable Assertion. CVSS score: 4.7/10. Published 2026-11-09.

How severe is CVE-2026-125246?

Medium severity. CVSS v3 base score is 4.7 out of 10.

Vulnerability in Ffmpeg

CVE-2026-125246

FFmpeg through 9.0.2 contains a denial of service vulnerability in cbs_jpeg_assemble_fragment() that miscounts 0xff stuffing bytes in JPEG scan headers. Attackers can supply a crafted JPEG/MJPEG stream with 0xff in the scan header, triggering an av_assert0 abort when CBS-based bitstream filters process it.

Published 2026-11-09.

CVSS v3 metric

CVSS v3 base score 4.7 (Medium). Vector: CVSS:3.1/AV:L/AC:H/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

Ffmpeg

Weakness classification (CWE)

CWE-617 — Reachable Assertion

References

code.ffmpeg.org/FFmpeg/FFmpeg/pulls/25232 (issue-tracking)
github.com/FFmpeg/FFmpeg (product)
github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/cbs_jpeg.c (technical-description)
Patch Commit (patch)
VulnCheck Advisory: FFmpeg through 9.0.2 Assertion Failure DoS via cbs_jpeg_assemble_fragment (third-party-advisory)

Frequently asked questions

What is CVE-2026-125246?: CVE-2026-125246 is a medium-severity vulnerability in Ffmpeg, classified under Reachable Assertion. CVSS score: 4.7/10. Published 2026-11-09.
How severe is CVE-2026-125246?: Medium severity. CVSS v3 base score is 4.7 out of 10.