User Impersonation Affecting puma package, versions >=5.5.0, <7.2.1>=8.0.0, <8.0.2
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Test your applications- Snyk IDSNYK-RUBY-PUMA-17220028
- published7 Jun 2026
- disclosed5 Jun 2026
- creditandy hex,Nate Berkopec
Introduced: 5 Jun 2026
NewCVE-2026-47737 (opens in a new tab)How to fix?
Upgrade puma to version 7.2.1, 8.0.2 or higher.
Overview
puma is a simple, fast, threaded, and highly concurrent HTTP 1.1 server for Ruby/Rack applications. Puma is intended for use in both development and production environments. It's great for highly concurrent Ruby implementations such as Rubinius and JRuby as well as as providing process worker support to support CRuby well.
Affected versions of this package are vulnerable to User Impersonation via PROXY protocol v1 spoofing. When set_remote_address proxy_protocol: :v1 is set, an attacker can spoof the source IP address by injecting additional PROXY headers between HTTP requests on the same persistent connection, causing the application to treat the injected header as authoritative and overwrite the REMOTE_ADDR value.
Workaround
This vulnerability can be avoided by setting enable_keep_alives false to disable persistent connections entirely.