Puma is a simple, fast, multi-threaded, parallel HTTP 1.1 server for Ruby/Rack applications. When using Puma behind a proxy that does not properly validate that the incoming HTTP request matches the RFC7230 standard, Puma and the frontend proxy may disagree on where a request starts and ends. This would allow requests to be smuggled via the front-end proxy to Puma. The vulnerability has been fixed in 5.6.4 and 4.3.12. Users are advised to upgrade as soon as possible. Workaround: when deploying a proxy in front of Puma, turning on any and all functionality to make sure that the request matches the RFC7230 standard.
3.12.0-2ubuntu13.12.0-4ubuntu13.12.4-1ubuntu23.12.4-1ubuntu2+esm14.3.6-1ubuntu45.5.2-2ubuntu24.3.6-1ubuntu45.5.2-2ubuntu25.5.2-2ubuntu2+esm13.12.0-2ubuntu13.12.0-4ubuntu13.12.4-1ubuntu2Exploitability
AV:NAC:LPR:NUI:NScope
S:UImpact
C:HI:HA:NCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N