CVE-2026-126085 Active Storage: Possible circumvention of file size limits in Active Storage direct uploads to Google Cloud Storage
- Exploited in the wild
- Not known
- Fix
- Available
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
Which versions are affected by CVE-2026-126085?
2 open source packages ship an affected version, including activestorage.
| Package | 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.
Sources
Also known as DEBIAN-CVE-2026-126085, GHSA-hfr4-8rjc-97m2, UBUNTU-CVE-2026-126085.