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CVE-2026-126186VulnerabilityPublished

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

Affects activestorageSource GCVE Database

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Authoritative record:CVE-2026-126186· High 8.8

Not known to be exploited · CVSS 8.8 High : upgrade to 8.1.4.1 soon.

Data as of 10 Nov 2026, 22:36 UTC

CVSS 3.1 base score
8.8High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (GitHub_M)CVSS 3.18.8
Patch
Available – fixed in 8.1.4.1, 8.0.5.2
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 10 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

What to do

Upgrade activestorage to 8.1.4.1; activestorage to 8.0.5.2.

Affected software

ProductAffectedFixed in
RubyGemsactivestorageAffected
  • >=8.1.0.beta1 <8.1.4.1
Fixed in
  • 8.1.4.1
RubyGemsactivestorageAffected
  • <8.0.5.2
Fixed in
  • 8.0.5.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade Active Storage to version 8.0.5.2 or later, or 8.1.4.1 or later, where the vulnerability is fixed. For applications unable to upgrade immediately, remove ActiveStorage::Previewer::VideoPreviewer from config.active_storage.previewers and ActiveStorage::Analyzer::VideoAnalyzer and ActiveStorage::Analyzer::AudioAnalyzer from config.active_storage.analyzers to prevent FFmpeg from processing uploaded files. Running FFmpeg builds without AviSynth support mitigates the AviSynth attack vector but does not address other extension-based decoder risks in ImageMagick. Applications meeting the AviSynth conditions should consider all secrets potentially exposed and rotate them, including secret_key_base, master key, credentials, service credentials, database credentials, and third-party tokens. Changing secret_key_base also invalidates active sessions and signed cookies. Do not retain any exposed secrets as fallback.

Description

Active Storage versions prior to 8.0.5.2 and between 8.1.0.beta1 and 8.1.4.1 are vulnerable to arbitrary file read and potential remote code execution via crafted video previews, analysis, and image processing. The vulnerability arises because the tempfile used for uploaded blobs retains the original file extension, which influences how external tools like FFmpeg and ImageMagick decode the file. An attacker controlling the filename and content type can cause these tools to execute unintended decoders, including AviSynth scripts in FFmpeg builds with AviSynth support, potentially leading to file disclosure or remote code execution. Fixed versions restrict the tempfile extension to those matching the blob's content type, mitigating this risk.

References

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