Integer overflow in Ffmpeg
CVE-2026-125197
FFmpeg through 9.0.2 contains an integer underflow in decode_frame() in libavcodec/lcldec.c that allows attackers to trigger a heap out-of-bounds read via short ZLIB packets with FLAG_MULTITHREAD. Attackers can supply a crafted AVI or MKV file with an LCL video stream whose packet is shorter than 8 bytes, bypassing length clamping to crash the decoding application.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/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/25020 (issue-tracking)
- github.com/FFmpeg/FFmpeg (product)
- github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/lcldec.c (technical-description)
- github.com/FFmpeg/FFmpeg/commit/12e5d4ec98b7add7bcac9d8131d9a6dfb2549966 (patch)
- www.vulncheck.com/advisories/ffmpeg-through-9.0.2-heap-out-of-bounds-read-via-l… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-125197?
- CVE-2026-125197 is a medium-severity vulnerability in Ffmpeg, classified under Integer Underflow. CVSS score: 6.1/10. Published 2026-11-09.
- How severe is CVE-2026-125197?
- Medium severity. CVSS v3 base score is 6.1 out of 10.