RubySec

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CVE-2018-16477 (activestorage): Bypass vulnerability in Active Storage

ADVISORIES

GEM

activestorage

FRAMEWORK

rails

SEVERITY

CVSS v3: 6.5 (Medium)

UNAFFECTED VERSIONS

  • < 5.2.0

PATCHED VERSIONS

  • >= 5.2.1.1

DESCRIPTION

There is a vulnerability in Active Storage. This vulnerability has been assigned the CVE identifier CVE-2018-16477.

Versions Affected: >= 5.2.0 Not affected: < 5.2.0 Fixed Versions: 5.2.1.1

Impact

Signed download URLs generated by ActiveStorage for Google Cloud Storage service and Disk service include content-disposition and content-type parameters that an attacker can modify. This can be used to upload specially crafted HTML files and have them served and executed inline. Combined with other techniques such as cookie bombing and specially crafted AppCache manifests, an attacker can gain access to private signed URLs within a specific storage path.

Vulnerable apps are those using either GCS or the Disk service in production. Other storage services such as S3 or Azure aren’t affected.

All users running an affected release should either upgrade or use one of the workarounds immediately. For those using GCS, it’s also recommended to run the following to update existing blobs:

ActiveStorage::Blob.find_each do |blob|
  blob.send :update_service_metadata
end