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High, CVSS 8.8amended

Active Storage: Possible arbitrary file read and remote code execution in video previews, analysis and image processing

CVE-2026-126186GHSA-v924-7rp8-4mxh

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (activestorage 8.1.4.1, 8.0.5.2), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • RubyGems activestorage

    Affected
    >= 8.1.0.beta1, < 8.1.4.1< 8.0.5.2
    Fixed in
    8.0.5.2, 8.1.4.1

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
8.8 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

Impact `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.

Details The fixed releases keep the uploaded extension on the…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from osv record GHSA-v924-7rp8-4mxh

  2. Revision 1 · created ·

    Published from ghsa record GHSA-v924-7rp8-4mxh

Agent brief

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# Patch Next advisory brief: CVE-2026-126186

Advisory: Active Storage: Possible arbitrary file read and remote code execution in video previews, analysis and image processing
IDs: CVE-2026-126186, GHSA-v924-7rp8-4mxh
Record: https://patchnext.com/advisories/cve-2026-126186 (revision 2, source checked 11 Nov 2026, 07:35 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: activestorage 8.1.4.1, 8.0.5.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems activestorage: affected >= 8.1.0.beta1, < 8.1.4.1; < 8.0.5.2; fixed in 8.0.5.2, 8.1.4.1

## Suggested inspection (read-only)
- RubyGems activestorage: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on activestorage.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-v924-7rp8-4mxh (GitHub-reviewed advisory GHSA-v924-7rp8-4mxh lists affected ranges: RubyGems activestorage >=8.1.0.beta1 =0 <8.0.5.2)
- Verified: https://osv.dev/vulnerability/GHSA-v924-7rp8-4mxh (OSV record GHSA-v924-7rp8-4mxh lists affected ranges: RubyGems activestorage >=8.1.0.beta1 =0 <8.0.5.2 (fixed))

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