# CVE-2026-126188: Active Storage: Possible local file disclosure in Active Storage video previews and analysis


- **Severity:** Low 3.7 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 10 Nov 2026
- **Updated:** 12 Nov 2026
- **Also known as:** DEBIAN-CVE-2026-126188, GHSA-3f4q-8x5m-76v8, UBUNTU-CVE-2026-126188

## What is CVE-2026-126188?

CVE-2026-126188 is a low-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 8.0.5.2 and from 8.1 until 8.1.4.1, Active Storage's ActiveStorage::Previewer::VideoPreviewer, ActiveStorage::Analyzer::VideoAnalyzer, and ActiveStorage::Analyzer::AudioAnalyzer pass uploaded blob contents to FFmpeg without restricting the demuxer. A direct upload can retain a client-declared video/* or audio/* content type for an HLS playlist. FFmpeg content probing selects the hls demuxer, which opens attacker-named file:// segments when the blob is previewed or analyzed. Applications that accept untrusted uploads and generate video previews or analyze video or audio attachments can disclose a local media file readable by the application process when the attacker knows its path. This issue is fixed in versions 8.0.5.2 and 8.1.4.1.

Weakness: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)

## Which versions are affected by CVE-2026-126188?

2 open source packages ship an affected version, including activestorage.


| Package | Ecosystem | 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-2026-126188?

Upgrade activestorage to a fixed version for your release line: 8.0.5.2 or 8.1.4.1.

## Is CVE-2026-126188 being exploited?

There is no known exploitation of CVE-2026-126188 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-126188 and fix it if it is affected.

What it is: CVE-2026-126188 is a low-severity vulnerability in rails, published on 10 Nov 2026. 
Exploitation: There is no known exploitation of CVE-2026-126188 in the wild and no public exploit code.

Affected packages and fixed versions:
- activestorage (RubyGems): affected all versions; fixed in 8.0.5.2
- activestorage (RubyGems): affected from 8.1.0.beta1; fixed in 8.1.4.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-126188/ (Markdown: https://insights.sbomify.com/CVE-2026-126188/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-126188
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126188
- OSV: https://osv.dev/vulnerability/CVE-2026-126188

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-126188/
Summaries are generated and may contain mistakes; the official description above is the record.