CVE-2021-29509
puma - security update
Description
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.
How to fix CVE-2021-29509
To remediate CVE-2021-29509, upgrade the affected package to a fixed version below.
- —upgrade to 4.3.8-1 or later
- —upgrade to 3.12.0-2+deb10u3 or later
- —upgrade to 4.3.8 or later
Is CVE-2021-29509 being exploited?
Low — EPSS is 1.4%, meaning exploitation activity has not been observed at scale.
Affected packages (3)
- from 0, < 4.3.8-1
- from 0, < 3.12.0-2+deb10u3
- from 0, < 4.3.8
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | HIGH7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |