# CVE-2026-126074: Active Storage: Possible DoS vulnerability in Active Storage filename handling


- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 10 Nov 2026
- **Updated:** 10 Nov 2026
- **Also known as:** DEBIAN-CVE-2026-126074, GHSA-p2pm-g2h6-7j5j, UBUNTU-CVE-2026-126074

## What is CVE-2026-126074?

CVE-2026-126074 is a medium-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::Filename#base and #extension_with_delimiter, and therefore #extension, pass the stored filename unmodified to File.basename and File.extname, which raise ArgumentError when the name contains a NUL byte. Active Storage stores the client-supplied filename verbatim, so a user who is permitted to upload an attachment could persist such a filename on databases that accept NUL bytes in string columns, such as SQLite and MySQL/MariaDB. Each subsequent request that builds a variant or preview of the blob, opens it, or renders it as an Action Text attachment then raises, possibly resulting in a persistent DoS vulnerability for the pages that display the blob until it is purged or its filename is corrected. Applications that use PostgreSQL are not affected, because PostgreSQL rejects the row. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.

Weakness: CWE-248 (Uncaught Exception)

## Which versions are affected by CVE-2026-126074?

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-2026-126074?

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

## Is CVE-2026-126074 being exploited?

There is no known exploitation of CVE-2026-126074 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-126074 and fix it if it is affected.

What it is: CVE-2026-126074 is a medium-severity vulnerability in rails, published on 10 Nov 2026. 
Exploitation: There is no known exploitation of CVE-2026-126074 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-2026-126074/ (Markdown: https://insights.sbomify.com/CVE-2026-126074/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-126074
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126074
- OSV: https://osv.dev/vulnerability/CVE-2026-126074

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-126074/
Summaries are generated and may contain mistakes; the official description above is the record.