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, when a GCS service is configured with the cache_control option, ActiveStorage::Service::GCSService#url_for_direct_upload signs direct-upload URLs with V4, and the V4 signature covers only the Cache-Control and Host headers. A direct-upload client can therefore send a Content-Type of its choosing, and can omit the declared Content-MD5, without invalidating the URL. GCS stores the supplied content type as object metadata, which takes precedence over the response-content-type that Active Storage sets on download URLs, so an uploaded object could be served as inline HTML under the application's bucket path on storage.googleapis.com. Script in such an object runs on the storage origin rather than the application's, but could register a Service Worker scoped to the bucket path and read or replace a victim's later responses for signed URLs in that bucket. Applications that use the GCS service with cache_control configured and accept direct uploads are affected. GCS services without cache_control sign with V2 and are not affected. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.

Affected: RubyGems: activestorage

### Impact When a GCS service is configured with the `cache_control` option, `ActiveStorage::Service::GCSService#url_for_direct_upload` signs direct-upload URLs with V4, and the V4 signature covers only the `Cache-Control` and `Host` headers. A direct-upload client can therefore send a `Content-Type` of its choosing, and can omit the declared `Content-MD5`, without invalidating the URL. GCS stores the supplied content type as object metadata, which takes precedence over the `response-content-type` that Active Storage sets on download URLs, so an uploaded object could be served as inline HTML under the application's bucket path on `storage.googleapis.com`. Script in such an object runs on the storage origin rather than the application's, but could register a Service Worker scoped to the bucket path and read or replace a victim's later responses for signed URLs in that bucket.

Applications that use the GCS service with `cache_control` configured and accept direct uploads are affected. GCS services without `cache_control` sign with V2 and are not affected.

### Details The fixed releases sign every GCS direct-upload URL with V2, which binds an empty `Content-Type` and the declared `Content-MD5`. The configured `Cache-Control` is still returned by `headers_for_direct_upload` and sent by the client, but it is no longer part of the signature, and direct-upload URLs for these services are no longer limited to V4's seven-day maximum expiry. See the Active Storage CHANGELOG.

### Wo…

Affected: Ubuntu:Pro:16.04:LTS: rails, Ubuntu:Pro:18.04:LTS: rails, Ubuntu:Pro:20.04:LTS: rails, Ubuntu:Pro:22.04:LTS: rails, Ubuntu:24.04:LTS: rails, Ubuntu:26.10: rails, Ubuntu:26.04:LTS: rails

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, when a GCS service is configured with the cache_control option, ActiveStorage::Service::GCSService#url_for_direct_upload signs direct-upload URLs with V4, and the V4 signature covers only the Cache-Control and Host headers. A direct-upload client can therefore send a Content-Type of its choosing, and can omit the declared Content-MD5, without invalidating the URL. GCS stores the supplied content type as object metadata, which takes precedence over the response-content-type that Active Storage sets on download URLs, so an uploaded object could be served as inline HTML under the application's bucket path on storage.googleapis.com. Script in such an object runs on the storage origin rather than the application's, but could register a Service Worker scoped to the bucket path and read or replace a victim's later responses for signed URLs in that bucket. Applications that use the GCS service with cache_control configured and accept direct uploads are affected. GCS services without cache_control sign with V2 and are not affected. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.

Ein Angreifer kann mehrere Schwachstellen in Ruby on Rails ausnutzen, um beliebigen Programmcode auszuführen, um einen Denial of Service Angriff durchzuführen, um Informationen offenzulegen, um Daten zu manipulieren, um falsche Informationen darzustellen, um einen Cross-Site Scripting Angriff durchzuführen und um Sicherheitsvorkehrungen zu umgehen.