Active Storage: Unsigned Content-Type in Active Storage GCS direct uploads with cache_control

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-126084
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-10 21:19:27 UTC
Updated2026-11-10 21:19:27 UTC
DescriptionActive 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.

Risk And Classification

Primary CVSS: v3.1 4.7 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N

Problem Types: CWE-345 | CWE-345 CWE-345: Insufficient Verification of Data Authenticity

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary4.7MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N
3.1CNADECLARED4.7MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Rails Rails affected >= 8.1, < 8.1.4.1 Not specified
CNA Rails Rails affected < 8.0.5.2 Not specified

References

ReferenceSourceLinkTags
github.com/rails/rails/security/advisories/GHSA-3w93-6hmw-whh4 [email protected] github.com
github.com/rails/rails/commit/ddc08ba61a8001e7402864c62e466cf732fc7614 [email protected] github.com
github.com/rails/rails/releases/tag/v8.1.4.1 [email protected] github.com
github.com/rails/rails/releases/tag/v8.0.5.2 [email protected] github.com
github.com/rails/rails/commit/8d93f6a872e9550a91bf0e4fce50083a235ef3b1 [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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