Quick answers
- Is CVE-2026-125259 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-125259 being exploited in the wild.
- How severe is CVE-2026-125259?
- High severity, with a CVSS score of 7.8, published 9 November 2026.
- Which products and versions are affected?
- Ffmpeg through 9.0.2.
- Is there a fix for CVE-2026-125259?
- Yes: fixed in FFmpeg 9.1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-125259 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-125259?
- 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
Technical details
The ff_prores_kostya_encode_init() function in FFmpeg uses 32-bit arithmetic to calculate frame_size_upper_bound, causing an integer overflow when processing large frame dimensions. This leads to an undersized packet buffer allocation; when encode_frame() subsequently writes slices to this buffer, it overflows and corrupts heap memory. The vulnerability requires attacker-controlled video input and affects video transcoding workflows using the prores_ks encoder.
Affected products
- FFmpeg FFmpeg through 9.0.2
Timeline
- 2026-11-09: disclosed
- 2026-10-30: patched: Fix merged to master branch prior to public disclosure