CVE-2024-21647: Puma

High severity, CVSS 7.5. EPSS: 1% chance of exploitation in the next 30 days.

Puma is a web server for Ruby/Rack applications built for parallelism. Prior to version 6.4.2, puma exhibited incorrect behavior when parsing chunked transfer encoding bodies in a way that allowed HTTP request smuggling. Fixed versions limits the size of chunk extensions. Without this limit, an attacker could cause unbounded resource (CPU, network bandwidth) consumption. This vulnerability has been fixed in versions 6.4.2 and 5.6.8.

Affected products

• Puma Puma: before 5.6.8 (fixed in 5.6.8); from 6.0.0, before 6.4.2 (fixed in 6.4.2)

Published 2024-01-08. Last modified 2026-06-17.