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No exploitation reportedFix availableAwaiting NVD analysis

CVE-2026-126186

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

No exploitation reported by the sources we read.

  • Published2026-11-10
  • Fixed in8.1.4.1 · 8.0.5.2
  • WeaknessCWE-646

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2026-11-1021:14CVE publishedCNA

Versions per branch

OSV
activestorage
BranchAffectedFixed in
8.1≥ 8.1.0.beta1, < 8.1.4.18.1.4.1
8.0< 8.0.5.28.0.5.2

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA1 product

As GitHub_M, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • rails
    Affected
    • = >= 8.1, < 8.1.4.1no fix stated
    • = < 8.0.5.2no fix stated

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-11-10

Fix

  1. Update activestorage to 8.1.4.1 · 8.0.5.2

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Metasploit modules
none listed
Metasploit Framework

Sources

  • CNACVSS 3.18.82026-11-10
  • CNAweakness (CWE)CWE-6462026-11-10
  • NVDweakness (CWE)CWE-646read 2026-11-10
  • OSVaffected packages—
  • GitHub AdvisoriesadvisoryHIGH2026-11-10

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Published
2026-11-10
Last Modified
2026-11-10
NVD status
Received
GitHub Advisory
GHSA-v924-7rp8-4mxh

Frequently asked questions

What is CVE-2026-126186?

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.

Is CVE-2026-126186 actively exploited?

Active exploitation of CVE-2026-126186 has not been confirmed.

What is the CVSS score for CVE-2026-126186?

CVE-2026-126186 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

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