{"id":"CVE-2021-29509","details":"Puma is a concurrent HTTP 1.1 server for Ruby/Rack applications. 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. This problem has been fixed in `puma` 4.3.8 and 5.3.1. 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 and a git patch is available for those using unsupported versions of Puma.","aliases":["GHSA-q28m-8xjw-8vr5"],"modified":"2026-04-10T04:32:47.082343Z","published":"2021-05-11T17:15:07.627Z","related":["GHSA-q28m-8xjw-8vr5","SUSE-SU-2021:2761-1","SUSE-SU-2021:2914-1","SUSE-SU-2022:1515-1","openSUSE-SU-2024:12592-1","openSUSE-SU-2024:13166-1","openSUSE-SU-2024:13721-1"],"references":[{"type":"ADVISORY","url":"https://rubygems.org/gems/puma"},{"type":"ADVISORY","url":"https://security.gentoo.org/glsa/202208-28"},{"type":"ADVISORY","url":"https://github.com/puma/puma/security/policy"},{"type":"ADVISORY","url":"https://lists.debian.org/debian-lts-announce/2022/08/msg00015.html"},{"type":"FIX","url":"https://gist.github.com/nateberkopec/4b3ea5676c0d70cbb37c82d54be25837"},{"type":"FIX","url":"https://github.com/puma/puma/security/advisories/GHSA-q28m-8xjw-8vr5"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/puma/puma","events":[{"introduced":"0"},{"fixed":"b911c13f8797aacaa8decf8532d6d7d45fda334f"},{"introduced":"13e18e8078c800adfc52af687acc1d8de5f3988d"},{"fixed":"1c91a4f1af23328118dbfe5b615f812af5e817ef"}],"database_specific":{"versions":[{"introduced":"0"},{"fixed":"4.3.8"},{"introduced":"5.0.0"},{"fixed":"5.3.1"}]}}],"versions":["v1.1.0","v1.1.1","v1.2.0","v1.2.1","v1.2.2","v1.3.0","v1.3.1","v1.4.0","v1.5.0","v2.0.0","v2.0.0.b2","v2.0.0.b3","v2.0.0.b4","v2.0.0.b5","v2.0.0.b6","v2.0.0.b7","v2.0.1","v2.1.0","v2.1.1","v2.10.0","v2.10.1","v2.10.2","v2.11.0","v2.11.2","v2.11.3","v2.12.0","v2.12.1","v2.12.2","v2.12.3","v2.13.0","v2.13.1","v2.13.2","v2.13.3","v2.13.4","v2.14.0","v2.15.0","v2.15.1","v2.15.2","v2.15.3","v2.16.0","v2.2.0","v2.2.1","v2.2.2","v2.3.0","v2.3.1","v2.3.2","v2.4.0","v2.4.1","v2.5.0","v2.5.1","v2.6.0","v2.7.0","v2.7.1","v2.8.1","v2.8.2","v2.9.0","v2.9.1","v2.9.2","v3.0.0","v3.0.0.rc1","v3.0.1","v3.0.2","v3.1.0","v3.1.1","v3.10.0","v3.11.0","v3.11.1","v3.11.2","v3.11.3","v3.11.4","v3.12.0","v3.2.0","v3.3.0","v3.4.0","v3.5.0","v3.5.1","v3.5.2","v3.6.0","v3.7.1","v3.8.0","v3.9.0","v3.9.1","v4.0.0","v4.0.1","v4.1.0","v4.2.0","v4.2.1","v4.3.0","v4.3.1","v4.3.2","v4.3.3","v4.3.4","v4.3.5","v4.3.6","v4.3.7","v5.0.0","v5.0.1","v5.0.2","v5.0.3","v5.1.0","v5.2.0","v5.2.1","v5.2.2","v5.3.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-29509.json","unresolved_ranges":[{"events":[{"introduced":"0"},{"last_affected":"10.0"}]}]}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}