Puma used with Rails may lead to Information Exposure
### Impact
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.
From Rails:
> Under certain circumstances response bodies will not be closed, for example a bug in a webserver[1] or a bug in a Rack middleware. In the event a response is not notified of a close, ActionDispatch::Executor will not know to reset thread local state for the next request. This can lead to data being leaked to subsequent requests, especially when interacting with ActiveSupport::CurrentAttributes.
The combination of these two behaviors (Puma not closing the body + Rails' Executor implementation) causes information leakage.
### Patches
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.
See:
https://github.com/advisories/GHSA-wh98-p28r-vrc9
for details about the rails vulnerability
Upgrading to a patched Rails _or_ Puma version fixes the vulnerability.
### Workarounds
Upgrade to Rails versions 7.02.2, 6.1.4.6, 6.0.4.6, and 5.2.6.2.
The Rails CVE
https://groups.google.com/g/ruby-security-ann/c/FkTM-_7zSNA/m/K2RiMJBlBAAJ?utm_medium=email&utm_source=footer&pli=1 includes a middleware that can be used instead.
### References
* Rails CVE: CVE-2022-23633
https://groups.google.com/g/ruby-security-ann/c/FkTM-_7zSNA/m/K2RiMJBlBAAJ?utm_medium=email&utm_source=footer&pli=1
### For more information
If you have any questions or comments about this advisory:
* Open an issue in puma
https://github.com/puma/puma
* See our security policy
https://github.com/puma/puma/security/policy