CVE-2021-29509

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.

Weakness classification

• security-advisories@github.com: CWE-400
• nvd@nist.gov: CWE-667

Primary references

• security-advisories@github.com — Patch, Third Party Advisory
• security-advisories@github.com — Patch, Third Party Advisory
• security-advisories@github.com — Third Party Advisory
• security-advisories@github.com — Mailing List, Third Party Advisory
• security-advisories@github.com — Product, Third Party Advisory
• security-advisories@github.com — Third Party Advisory
• af854a3a-2127-422b-91ae-364da2661108 — Patch, Third Party Advisory
• af854a3a-2127-422b-91ae-364da2661108 — Patch, Third Party Advisory
• af854a3a-2127-422b-91ae-364da2661108 — Third Party Advisory
• af854a3a-2127-422b-91ae-364da2661108 — Mailing List, Third Party Advisory
• af854a3a-2127-422b-91ae-364da2661108 — Product, Third Party Advisory
• af854a3a-2127-422b-91ae-364da2661108 — Third Party Advisory