# CVE-2026-126085: Active Storage: Possible circumvention of file size limits in Active Storage direct uploads to Google Cloud Storage


- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 10 Nov 2026
- **Updated:** 10 Nov 2026
- **Also known as:** DEBIAN-CVE-2026-126085, GHSA-hfr4-8rjc-97m2, UBUNTU-CVE-2026-126085

## What is CVE-2026-126085?

CVE-2026-126085 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::Service::GCSService#url_for_direct_upload does not bind the declared content length into the signed direct-upload URL, and #headers_for_direct_upload returns no length constraint, so the URL authorizes an upload body of any size. A direct-upload client could store a file larger than the byte_size it declared, and the resulting blob keeps the declared size, possibly bypassing application file size validations and quotas. This is the weakness that CVE-2020-8162 fixed in the S3 service. Applications that store files in Google Cloud Storage and accept direct uploads are affected. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.

Weakness: CWE-602 (Client-Side Enforcement of Server-Side Security)

## Which versions are affected by CVE-2026-126085?

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-2026-126085?

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

## Is CVE-2026-126085 being exploited?

There is no known exploitation of CVE-2026-126085 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-126085 and fix it if it is affected.

What it is: CVE-2026-126085 is a medium-severity vulnerability in rails, published on 10 Nov 2026. 
Exploitation: There is no known exploitation of CVE-2026-126085 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-2026-126085/ (Markdown: https://insights.sbomify.com/CVE-2026-126085/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-126085
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126085
- OSV: https://osv.dev/vulnerability/CVE-2026-126085

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-126085/
Summaries are generated and may contain mistakes; the official description above is the record.