# CVE-2026-120243: FFmpeg uninitialized variable in Go2Meeting decoder

Source: https://junglewise.ai/threats/cve-2026-120243-ffmpeg-2-0-through-9-0-2-contains-a-use-of-uninitialized  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-01. Updated: 2026-11-01  
License: CC BY 4.0 with a link back

CVE-2026-120243 · Severity: medium · CVSS 5.5 · Published 2026-11-01

FFmpeg is a multimedia processing library used to decode and encode video and audio. A flaw in the Go2Meeting (G2M) video decoder allows attackers to craft malicious video files that leak sensitive stack memory, potentially exposing pointers or security tokens that could be used in further attacks.

Technologies: [Ffmpeg](https://junglewise.ai/threats/technologies/ffmpeg). Vendors: [Ffmpeg](https://junglewise.ai/threats/vendors/ffmpeg).

## Quick answers

**Is CVE-2026-120243 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-120243 being exploited in the wild.

**How severe is CVE-2026-120243?** Medium severity, with a CVSS score of 5.5, published 1 November 2026.

**Which products and versions are affected?** Ffmpeg 2.0 through 9.0.2.

**Is there a fix for CVE-2026-120243?** Yes: fixed in FFmpeg 9.1 and later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-120243 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-120243?** Check whether you run Ffmpeg at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in FFmpeg 9.1 and later

## Technical details

The Go2Meeting decoder in FFmpeg fails to validate palette indices when decoding Kempf tiles, allowing the kempf_restore_buf() function to copy uninitialized stack bytes into decoded output when processing out-of-range palette indices. An attacker can craft a G2M3 or G2M4 stream with a short palette to trigger this memory leak. The vulnerability was fixed by adding bounds checking on palette indices before access.

## Affected products

- FFmpeg FFmpeg 2.0 through 9.0.2

## Timeline

- 2026-11-01: disclosed
- 2026-10-10: patched

## References

- [https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24858](https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24858)
- [https://github.com/FFmpeg/FFmpeg](https://github.com/FFmpeg/FFmpeg)

## Related threats

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- [FFmpeg CDXL decoder use of uninitialized variable in HAM palette](https://junglewise.ai/threats/cve-2026-120246-ffmpeg-4-4-through-9-0-2-contains-a-use-of-uninitialized)
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- [FFmpeg PCX decoder heap memory leak via uninitialized buffer](https://junglewise.ai/threats/cve-2026-120244-ffmpeg-2-1-through-9-0-2-contains-a-use-of-uninitialized)
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