CVE-2022-23634: Information Exposure when using Puma with Rails

Severity: medium (CVSS 5.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-02-11 · updated 2026-06-17
Weakness: CWE-200

Description

Puma is a Ruby/Rack web server built for parallelism. 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. The combination of these two behaviors (Puma not closing the body + Rails' Executor implementation) causes information leakage. 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. Upgrading to a patched Rails _or_ Puma version fixes the vulnerability.

Affected products

Debian Linux: 9.0, 10.0, 11.0
Fedoraproject Fedora: 35, 36, 37
puma: before 4.3.11; from 5.0.0 before 5.6.2 — fixed in 4.3.11, 5.6.2
Ruby on Rails: from 5.0.0 before 5.2.6.2; from 6.0.0 before 6.0.4.6; from 6.1.0 before 6.1.4.6; from 7.0.0 before 7.0.2.2 — fixed in 5.2.6.2, 6.0.4.6, 6.1.4.6, 7.0.2.2
Rubygems Puma: from 5.0.0 before 5.6.2; before 4.3.11; 5.0.0, 5.0.1, 5.0.2, 5.0.3, 5.0.4, 5.1.0 (+138) — fixed in 5.6.2, 4.3.11

How to fix

Upgrade to a fixed version: puma 4.3.11, 5.6.2; Ruby on Rails 5.2.6.2, 6.0.4.6, 6.1.4.6, 7.0.2.2; Rubygems Puma 5.6.2, 4.3.11. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2022-23634 or the next vulnerability affects your stack