Is CVE-2026-125256 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-125256 being exploited in the wild.

How severe is CVE-2026-125256?

High severity, with a CVSS score of 7, published 9 November 2026.

Is there a fix for CVE-2026-125256?

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-2026-125256 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-125256?

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.

CVE-2026-125256: FFmpeg heap buffer overflow in Huffyuv encoder

CVE-2026-125256 · Severity: high · CVSS 7 · Published 2026-11-09

FFmpeg is a widely-used multimedia framework that encodes and transcodes video. A heap buffer overflow in the Huffyuv video encoder can corrupt memory and crash the application when processing maliciously crafted or abnormally-sized video files. Attackers can exploit this by supplying video narrower than 8 or 16 pixels to trigger out-of-bounds writes on RISC-V systems with RVV extensions enabled.

Technologies: Ffmpeg. Vendors: Ffmpeg.

Quick answers

Is CVE-2026-125256 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-125256 being exploited in the wild.
How severe is CVE-2026-125256?: High severity, with a CVSS score of 7, published 9 November 2026.
Which products and versions are affected?: Ffmpeg through 9.0.2.
Is there a fix for CVE-2026-125256?: 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-2026-125256 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-125256?: 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 vulnerability exists in the ff_llvidenc_diff_bytes_rvv() function in the RISC-V/RVV implementation of the Huffyuv encoder. Negative length values passed to this function cause heap buffer overflows when the encoder processes RGB video frames narrower than 8 or 16 pixels. The flaw is specific to RVV-enabled RISC-V builds and allows writes past the encoder's temporary buffer.

Affected products

FFmpeg FFmpeg through 9.0.2

Timeline

2026-11-09: disclosed
2026-10-30: patched: Fix merged in PR #25573

References

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