CVE-2020-11077: Debian Linux

High severity, CVSS 7.5. EPSS: 2.9% chance of exploitation in the next 30 days.

In Puma (RubyGem) before 4.3.5 and 3.12.6, a client could smuggle a request through a proxy, causing the proxy to send a response back to another unknown client. If the proxy uses persistent connections and the client adds another request in via HTTP pipelining, the proxy may mistake it as the first request's body. Puma, however, would see it as two requests, and when processing the second request, send back a response that the proxy does not expect. If the proxy has reused the persistent connection to Puma to send another request for a different client, the second response from the first client will be sent to the second client. This is a similar but different vulnerability from CVE-2020-11076. The problem has been fixed in Puma 3.12.6 and Puma 4.3.5.

Affected products

• Debian Debian Linux: version 9.0 only
• Fedoraproject Fedora: version 33 only
• Opensuse Leap: version 15.1 only; version 15.2 only
• Puma Puma: from 3.0.0, before 3.12.6 (fixed in 3.12.6); from 4.0.0, before 4.3.5 (fixed in 4.3.5)

Published 2020-05-22. Last modified 2026-06-17.