ruby-advisory-db/gems/puma/CVE-2026-47737.yml at master · rubysec/ruby-advisory-db · GitHub

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---
gem: puma
cve: 2026-47737
ghsa: 2vqw-3mp8-cgmx
url: https://www.cve.org/CVERecord/SearchResults?query=CVE-2026-47737
title: Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on
  Persistent Connections
date: 2026-05-27
description: |
  ## Impact

  Puma is vulnerable to source IP spoofing when set_remote_address
  proxy_protocol: :v1 is enabled and persistent connections are used.

  PROXY protocol v1 is a connection-level protocol. Support was added
  to Puma in v5.5.0. 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.

  This can mislead applications or middleware that use REMOTE_ADDR for
  security decisions, rate limiting, auditing, or allow/deny lists.

  Only deployments that explicitly enable PROXY protocol v1 are affected,
  and will have set:

    set_remote_address proxy_protocol: :v1

  Puma'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.

  ## Workarounds

  * Disable PROXY protocol v1 parsing if it is not required:

    # remove/comment this:
    # set_remote_address proxy_protocol: :v1

  Users can also disable persistent connections to Puma, for example:

    enable_keep_alives false
cvss_v3: 7.5
unaffected_versions:
  - "< 5.5.0"
patched_versions:
  - "~> 7.2.1"
  - ">= 8.0.2"
related:
  url:
    - https://www.cve.org/CVERecord/SearchResults?query=CVE-2026-47737
    - https://rubygems.org/gems/puma/versions/8.0.2
    - https://github.com/puma/puma/blob/main/History.md#802--2026-05-27
    - https://github.com/puma/puma/blob/main/History.md#721--2026-05-27
    - https://github.com/puma/puma/releases/tag/v8.0.2
    - https://github.com/puma/puma/releases/tag/v7.2.1
    - https://github.com/puma/puma/pull/2654
    - https://github.com/phires/go-guerrilla/security/advisories/GHSA-c2c3-pqw5-5p7c
    - https://github.com/puma/puma/issues/2651
    - https://rubyweekly.com/issues/803
    - https://github.com/puma/puma/security/advisories/GHSA-2vqw-3mp8-cgmx
notes: |
    - https://www.cve.org/CVERecord/SearchResults?query=CVE-2026-47737 (reserved)
    - No nvd cvss values