Is there a public exploit for CVE-2026-126084?

No public exploit for CVE-2026-126084 was found in Exploit-DB, Metasploit, Nuclei templates or public proof-of-concept repositories. That is an absence of evidence rather than proof that none exists.

How severe is CVE-2026-126084?

CVE-2026-126084 scores CVSS 4.7 (v3.1), rated medium. EPSS puts the chance of exploitation in the next 30 days at 0.14%.

What does CVE-2026-126084 affect?

CVE-2026-126084 affects rails rails.

4.7 Medium

Active Storage makes it simple to upload and reference files in cloud services and attach those files to Active Record objects.

CVE-2026-126084

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 cachecontrol option, ActiveStorage::Service::GCSService#urlfordirectupload 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 cachecontrol configured and accept direct uploads are affected. GCS services without cachecontrol sign with V2 and are not affected. This…

Assessment

CVSS: 4.7 (v3.1)
Severity: Medium
EPSS: 0.14% chance of exploitation in the next 30 days
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 10 November 2026
Last updated: 12 November 2026
Affected: rails · rails
Assigner: GitHub_M

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

At the source

EUVD (ENISA)

References

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