CVE-2026-126186 Active Storage: Possible arbitrary file read and remote code execution in video previews, analysis and image processing
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-126186?
CVE-2026-126186 is a high-severity vulnerability in rails, published on 10 Nov 2026.
Official description
Active Storage makes it simple to upload and reference files in cloud services and attach those files to Active Record objects. Prior to 8.1.4.1 and 8.0.5.2, ActiveStorage::Blob#open writes a blob to a tempfile whose name carries the extension of the uploaded filename, and hands that path to ffprobe (VideoAnalyzer, AudioAnalyzer), ffmpeg (VideoPreviewer) and ImageMagick (ImageAnalyzer, the :mini_magick variant processor). These tools select a decoder from the file extension when the content does not identify its own format, so an attacker who chooses the filename and declares the content type of an upload chooses which decoder processes it. An FFmpeg built with AviSynth support treats a file with the .avs extension as an AviSynth script and evaluates it, which could disclose files readable by the application process through the preview image, or load a native library the attacker has also uploaded, possibly leading to remote code execution in the FFmpeg process. ImageMagick selects its coders and delegates from the extension in the same way. An application is affected if it accepts uploads from untrusted users and analyzes video or audio attachments, generates video previews, or processes images with ImageMagick. The AviSynth attack additionally requires an FFmpeg built with --enable-avisynth and the AviSynthPlus runtime on the host. Upstream FFmpeg and the common Linux distribution and Homebrew packages do not enable it; the GPL builds distributed for Windows and Linux from ffmpeg.org do. Other decoders that FFmpeg or ImageMagick select from the extension may be reachable without AviSynth. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.
Weakness: CWE-646
Which versions are affected by CVE-2026-126186?
2 open source packages ship an affected version, including activestorage.
| Package | Affected | Fixed in |
|---|---|---|
activestorage RubyGems | All versions | 8.0.5.2 |
activestorage RubyGems | From 8.1.0.beta1 | 8.1.4.1 |
How do I fix CVE-2026-126186?
Upgrade activestorage to a fixed version for your release line: 8.0.5.2 or 8.1.4.1.
Is CVE-2026-126186 being exploited?
There is no known exploitation of CVE-2026-126186 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-126186, GHSA-v924-7rp8-4mxh, UBUNTU-CVE-2026-126186.