Puma is a Ruby/Rack web server built for parallelism. Prior to puma
version 5.6.2
, puma
may not always call close
on the response body. Rails, prior to version 7.0.2.2
, depended on the response body being closed in order for its CurrentAttributes
implementation to work correctly. The combination of these two behaviors (Puma not closing the body + Rails' Executor implementation) causes information leakage. This problem is fixed in Puma versions 5.6.2 and 4.3.11. This problem is fixed in Rails versions 7.02.2, 6.1.4.6, 6.0.4.6, and 5.2.6.2. Upgrading to a patched Rails or Puma version fixes the vulnerability.