Active Storage: Possible circumvention of file size limits in Active Storage direct uploads to Google Cloud Storage

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Impact `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.

Details The fixed releases sign an `x-goog-content-length-range` header that matches the blob's declared `byte_size` and return it from `headers_for_direct_upload`, so Cloud Storage rejects an upload body of any other size. Browsers send this header with the direct upload, so a bucket's CORS configuration must list `x-goog-content-length-range` in `responseHeader`, or browser…

Published by the source

10 Nov 2026, 21:37 UTC

Last modified by the source

10 Nov 2026, 21:45 UTC

Source last checked

11 Nov 2026, 07:35 UTC

1. Revision 2 · amended · 11 Nov 2026

   Amended from osv record GHSA-hfr4-8rjc-97m2

2. Revision 1 · created · 10 Nov 2026

   Published from ghsa record GHSA-hfr4-8rjc-97m2

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# Patch Next advisory brief: CVE-2026-126085

Advisory: Active Storage: Possible circumvention of file size limits in Active Storage direct uploads to Google Cloud Storage
IDs: CVE-2026-126085, GHSA-hfr4-8rjc-97m2
Record: https://patchnext.com/advisories/cve-2026-126085 (revision 2, source checked 11 Nov 2026, 07:35 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: activestorage 8.1.4.1, 8.0.5.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems activestorage: affected >= 8.1.0.beta1, < 8.1.4.1; < 8.0.5.2; fixed in 8.0.5.2, 8.1.4.1

## Suggested inspection (read-only)
- RubyGems activestorage: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on activestorage.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-hfr4-8rjc-97m2 (GitHub-reviewed advisory GHSA-hfr4-8rjc-97m2 lists affected ranges: RubyGems activestorage >=8.1.0.beta1 =0 <8.0.5.2)
- Verified: https://osv.dev/vulnerability/GHSA-hfr4-8rjc-97m2 (OSV record GHSA-hfr4-8rjc-97m2 lists affected ranges: RubyGems activestorage >=8.1.0.beta1 =0 <8.0.5.2 (fixed))

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