{"id":"CVE-2026-47737","aliases":["GHSA-2vqw-3mp8-cgmx"],"url":"https://o3.security/vulnerability/CVE-2026-47737","summary":"Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on Persistent Connections","details":"### Impact\n\nPuma is vulnerable to source IP spoofing when `set_remote_address proxy_protocol: :v1` is enabled and persistent connections are used.\n\nPROXY protocol v1 is a connection-level protocol. [Support was added to Puma in v5.5.0](https://github.com/puma/puma/issues/2651). A proxy sends one PROXY header at the beginning of a TCP connection, before any HTTP data. Puma incorrectly re-parsed PROXY protocol headers after each keep-alive request on the same connection. An attacker able to send HTTP requests through a trusted proxy could therefore inject a second PROXY header between HTTP requests. Puma would treat the injected header as authoritative for the next request and overwrite `REMOTE_ADDR`.\n\nThis can mislead applications or middleware that use `REMOTE_ADDR` for security decisions, rate limiting, auditing, or allow/deny lists.\n\n**Only deployments that explicitly enable PROXY protocol v1 are affected**, and will have set:\n\n```ruby\nset_remote_address proxy_protocol: :v1\n```\n\nPuma's default configuration is not affected. Deployments that do not use persistent connections to Puma are also not expected to be affected by this issue.\n\n### Patches\n\nUsers should upgrade to versions 7.2.1 or 8.0.2.\n\n### Workarounds\n\nDisable PROXY protocol v1 parsing if it is not required:\n\n ```ruby\n   # remove/comment this:\n   # set_remote_address proxy_protocol: :v1\n ```\n\nUsers can also disable persistent connections to Puma, for example:\n\n```ruby\nenable_keep_alives false\n```\n\n### References\n\n- [HAProxy PROXY protocol specification](https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt)\n- [CVE-2025-31135 / GHSA-c2c3-pqw5-5p7c: go-guerrilla repeated PROXY command source IP spoofing](https://github.com/phires/go-guerrilla/security/advisories/GHSA-c2c3-pqw5-5p7c)\n- [Puma `set_remote_address` documentation](https://github.com/puma/puma/blob/master/lib/puma/dsl.rb)","published":"2026-07-14T19:45:16.648Z","modified":"2026-08-12T03:51:36.316962906Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"},"epss":{"score":0.00266,"percentile":0.18015,"asOf":"2026-08-24"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"RubyGems","name":"puma","fixedVersion":"8.0.2"},{"ecosystem":"RubyGems","name":"puma","fixedVersion":"7.2.1"}],"fix":{"url":"https://github.com/puma/puma/commit/439c6136d9c2275721b7864db3ee78af7c80889f","label":"puma/puma@439c613"},"references":[{"type":"WEB","url":"https://github.com/puma/puma/releases/tag/v7.2.1"},{"type":"WEB","url":"https://github.com/puma/puma/releases/tag/v8.0.2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/47xxx/CVE-2026-47737.json"},{"type":"ADVISORY","url":"https://github.com/puma/puma/security/advisories/GHSA-2vqw-3mp8-cgmx"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-47737"},{"type":"FIX","url":"https://github.com/puma/puma/commit/439c6136d9c2275721b7864db3ee78af7c80889f"},{"type":"FIX","url":"https://github.com/puma/puma/commit/ebe9db3929ab8299d19c8f5b41e8ef4f4b22fa58"},{"type":"FIX","url":"https://github.com/puma/puma/pull/3944"},{"type":"FIX","url":"https://github.com/puma/puma/pull/3947"},{"type":"PACKAGE","url":"https://github.com/puma/puma"},{"type":"WEB","url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/puma/CVE-2026-47737.yml"},{"type":"WEB","url":"https://www.cve.org/CVERecord/SearchResults?query=CVE-2026-47737"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:36.316962906Z"}}