---
id: CVE-2026-47736
aliases:
  - GHSA-qpgp-93vx-g8v8
title: 'Puma PROXY Protocol v1 Parser Allows Remote Memory Exhaustion '
summary: 'Puma PROXY Protocol v1 Parser Allows Remote Memory Exhaustion '
severity: high
cvss: 7.5
cwe:
  - CWE-400
vendor: puma
product: puma
ecosystem: rubygems
affected:
  - 'puma >= 8.0.0, < 8.0.2'
  - 'puma >= 5.5.0, < 7.2.1'
patched:
  - puma 8.0.2
  - puma 7.2.1
published: '2026-06-08'
updated: '2026-06-08'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-qpgp-93vx-g8v8'
references:
  - url: 'https://github.com/puma/puma/security/advisories/GHSA-qpgp-93vx-g8v8'
  - url: >-
      https://github.com/rubysec/ruby-advisory-db/blob/master/gems/puma/CVE-2026-47736.yml
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-47736'
  - url: 'https://github.com/advisories/GHSA-qpgp-93vx-g8v8'
tags:
  - ghsa
  - rubygems
ingestedAt: '2026-07-07T15:41:59.610Z'
epss: 0.0063
epssPercentile: 0.48831
---

## Overview

### Impact

[PROXY protocol support for Puma](https://github.com/puma/puma/issues/2651) was added in version 5.5.0.

When PROXY protocol v1 support is enabled, Puma reads incoming bytes into an internal buffer. It waits for "\r\n" to determine whether a PROXY v1 line is present. If an attacker opens a TCP connection and continuously sends bytes without CRLF, Puma keeps appending to this pre-parse buffer.

This can cause unbounded in-process memory growth and additional CPU cost from repeatedly scanning the growing buffer for CRLF. A single, unauthenticated TCP connection can drive significant memory growth and may cause process/container OOM or degraded availability.

**Only Puma servers using the following non-default config are affected:**

```ruby
   set_remote_address proxy_protocol: :v1
```

### Patches

Users should upgrade to versions 7.2.1 or 8.0.2.

### Workarounds

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

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

 - Restrict direct network access to Puma listeners using PROXY protocol:
     - Only allow trusted load balancers/reverse proxies to connect.
     - Block arbitrary client TCP access with firewall/security group rules.

### Resources
- [HAProxy PROXY protocol specification](https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt)
- [CWE-400: Uncontrolled Resource Consumption](https://cwe.mitre.org/data/definitions/400.html)
- [CWE-770: Allocation of Resources Without Limits or Throttling](https://cwe.mitre.org/data/definitions/770.html)
- [Puma `set_remote_address` documentation](https://github.com/puma/puma/blob/master/lib/puma/dsl.rb)
- [Puma client PROXY protocol parsing code](https://github.com/puma/puma/blob/master/lib/puma/client.rb)
- [Puma constants, including `PROXY_PROTOCOL_V1_REGEX`](https://github.com/puma/puma/blob/master/lib/puma/const.rb)

## Affected packages

- `puma >= 8.0.0, < 8.0.2`
- `puma >= 5.5.0, < 7.2.1`

## Remediation

Upgrade to a patched release:

- `puma 8.0.2`
- `puma 7.2.1`