GHSA-q28m-8xjw-8vr5 Puma's Keepalive Connections Causing Denial Of Service

• RubyGems puma: < 4.3.8 → fixed in 4.3.8 • RubyGems puma: >= 5.0.0, < 5.3.1 → fixed in 5.3.1

This vulnerability is related to CVE-2019-16770. Impact The fix for CVE-2019-16770 was incomplete. The original fix only protected existing connections that had already been accepted from having their requests starved by greedy persistent-connections saturating all threads in the same process. However, new connections may still be starved by greedy persistent-connections saturating all threads in all processes in the cluster. A `puma` server which received more concurrent `keep-alive` connections than the server had threads in its threadpool would service only a subset of connections, denying service to the unserved connections. Patches This problem has been fixed in `puma` 4.3.8 and 5.3.1. Workarounds Setting `queue_requests false` also fixes the issue. This is not advised when using `puma` without a reverse proxy, such as `nginx` or `apache`, because you will open yourself to slow client attacks (e.g. slowloris)). The fix is very small. A git patch is available here for those using unsupported versions of Puma. For more information If you have any questions or comments about this advisory: • Open an issue in Puma. • To report problems with this fix or to report another vulnerability, see our security policy. Acknowledgements Thank you to @MSP-Greg, @wjordan and @evanphx for their review on this issue. Thank you to @ioquatix for providing a modified fork of `wrk` which made debugging this issue much easier.