# CVE-2026-47736: Puma uncontrolled resource consumption in PROXY protocol v1 parser

Source: https://junglewise.ai/threats/cve-2026-47736-puma-uncontrolled-resource-consumption-in-proxy-protocol-v1  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-14. Updated: 2026-07-14  
License: CC BY 4.0 with a link back

CVE-2026-47736 · Severity: high · CVSS 7.5 · Published 2026-07-14

Puma is a popular web server used to run Ruby applications. A vulnerability in its handling of the PROXY protocol allows an attacker to crash the server or significantly slow it down by sending a continuous stream of data without the expected line endings. This can lead to a total service outage (denial of service) as the server consumes all available memory and processor power trying to process the malicious request.

Technologies: [puma (RubyGems)](https://junglewise.ai/threats/technologies/puma). Vendors: [RubyGems](https://junglewise.ai/threats/vendors/rubygems).

## Quick answers

**Is CVE-2026-47736 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-47736 being exploited in the wild.

**How severe is CVE-2026-47736?** High severity, with a CVSS score of 7.5, published 14 July 2026.

**Which products and versions are affected?** puma (RubyGems) ECOSYSTEM:introduced=8.0.0,fixed=8.0.2.

**Is there a fix for CVE-2026-47736?** Yes. puma (RubyGems): upgrade to 8.0.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-47736 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-47736?** Check whether you run puma (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- puma (RubyGems): upgrade to 8.0.2 or later

  ```sh
  bundle update puma
  ```


## Technical details

Puma is vulnerable to uncontrolled resource consumption (CWE-400) within its PROXY protocol v1 parsing logic. When the 'proxy_protocol: :v1' configuration is enabled, the server reads incoming bytes into an internal pre-parse buffer while searching for a CRLF (\r\n) sequence. Because there is no limit on the size of this buffer before the CRLF is found, a remote, unauthenticated attacker can establish a TCP connection and send a continuous stream of bytes without line endings. This results in unbounded memory growth and high CPU usage as the server repeatedly scans the ever-increasing buffer. The vulnerability is resolved in versions 7.2.1 and 8.0.2 by enforcing maximum line lengths and anchoring the protocol regex.

## Affected products

- Puma Puma >= 5.5.0, < 7.2.1; >= 8.0.0, < 8.0.2

## Identifiers

- CVE-2026-47736
- GHSA-qpgp-93vx-g8v8

## Timeline

- 2026-05-27: advisory: GitHub Security Advisory published
- 2026-05-27: patched: Versions 7.2.1 and 8.0.2 released
- 2026-07-14: disclosed: CVE-2026-47736 published to NVD

## References

- [https://github.com/puma/puma/commit/439c6136d9c2275721b7864db3ee78af7c80889f](https://github.com/puma/puma/commit/439c6136d9c2275721b7864db3ee78af7c80889f)
- [https://github.com/puma/puma/commit/ebe9db3929ab8299d19c8f5b41e8ef4f4b22fa58](https://github.com/puma/puma/commit/ebe9db3929ab8299d19c8f5b41e8ef4f4b22fa58)
- [https://github.com/puma/puma/releases/tag/v7.2.1](https://github.com/puma/puma/releases/tag/v7.2.1)
- [https://github.com/puma/puma/releases/tag/v8.0.2](https://github.com/puma/puma/releases/tag/v8.0.2)
- [https://github.com/puma/puma/security/advisories/GHSA-qpgp-93vx-g8v8](https://github.com/puma/puma/security/advisories/GHSA-qpgp-93vx-g8v8)

## Related threats

- [Puma source IP spoofing via PROXY protocol injection](https://junglewise.ai/threats/cve-2026-47737-puma-source-ip-spoofing-via-proxy-protocol-injection)
- [Puma's header normalization allows for client to clobber proxy set headers](https://junglewise.ai/threats/cve-2024-45614-puma-s-header-normalization-allows-for-client-to-clobber-proxy)
- [Puma HTTP Request/Response Smuggling vulnerability](https://junglewise.ai/threats/cve-2024-21647-puma-http-request-response-smuggling-vulnerability)
- [Puma HTTP Request/Response Smuggling vulnerability](https://junglewise.ai/threats/cve-2023-40175-puma-http-request-response-smuggling-vulnerability)
- [Puma vulnerable to HTTP Request Smuggling](https://junglewise.ai/threats/cve-2022-24790-puma-vulnerable-to-http-request-smuggling)