CarrierWave content-Type allowlist bypass vulnerability which possibly leads to XSS remained

Impact

The vulnerability CVE-2023-49090
wasn’t fully addressed.

This vulnerability is caused by the fact that when uploading to
object storage, including Amazon S3, it is possible to set a
Content-Type value that is interpreted by browsers to be different
from what’s allowed by content_type_allowlist, by providing
multiple values separated by commas.

This bypassed value can be used to cause XSS.

Patches

Upgrade to 3.0.7 or 2.2.6.

Workarounds

Use the following monkey patch to let CarrierWave parse the
Content-type by using Marcel::MimeType.for.

# For CarrierWave 3.x
CarrierWave::SanitizedFile.class_eval do
  def declared_content_type
    @declared_content_type ||
      if @file.respond_to?(:content_type) && @file.content_type
        Marcel::MimeType.for(declared_type: @file.content_type.to_s.chomp)
      end
  end
end

# For CarrierWave 2.x
CarrierWave::SanitizedFile.class_eval do
  def existing_content_type
    if @file.respond_to?(:content_type) && @file.content_type
      Marcel::MimeType.for(declared_type: @file.content_type.to_s.chomp)
    end
  end
end

References

OWASP - File Upload Cheat Sheet