Vulnerability in Ffmpeg
CVE-2026-125257
FFmpeg through 9.0.2 contains an off-by-one heap overflow vulnerability in get_exponent_dynamic() in libavcodec/nellymoserenc.c that allows writing one element past the opt and path allocations. Attackers can supply crafted audio to applications encoding Nellymoser with trellis enabled, causing idx to equal OPT_SIZE and overwrite adjacent heap memory.
Published .
CVSS v3 metric
CVSS v3 base score 7.0 (High). Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/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/24471 (issue-tracking)
- github.com/FFmpeg/FFmpeg/commit/733bec3e19759520ccdbeb6c3c0cae280bbe6dc5 (patch)
- github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/nellymoserenc.c (technical-description)
- github.com/FFmpeg/FFmpeg (product)
- www.vulncheck.com/advisories/ffmpeg-through-9.0.2-heap-overflow-via-nellymoser-… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-125257?
- CVE-2026-125257 is a high-severity vulnerability in Ffmpeg, classified under Off-by-one Error. CVSS score: 7.0/10. Published 2026-11-09.
- How severe is CVE-2026-125257?
- High severity. CVSS v3 base score is 7.0 out of 10.