# CVE-2026-47736: puma: Puma is a Ruby/Rack web server built for parallelism

CVE-2026-47736 is fixed in puma on 1 platform, first by DEBIAN-CVE-2026-47736, released July 18, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-47736
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0035
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 14, 2026

## Description

Puma is a Ruby/Rack web server built for parallelism. From 5.5.0 until 7.2.1 and 8.0.2, when PROXY protocol v1 support is enabled, Puma reads incoming bytes into an internal buffer while waiting for CRLF to determine whether a PROXY v1 line is present, allowing an attacker that continuously sends bytes without CRLF to cause unbounded in-process memory growth and additional CPU cost from repeatedly scanning the growing buffer. This issue is fixed in versions 7.2.1 and 8.0.2.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | puma Debian 12.15 (bookworm) | 5.6.5-3+deb12u2 | [DEBIAN-CVE-2026-47736](https://patchblox.com/security/data/fix/linux/debian-cve-2026-47736.md) | Jul 18, 2026 |
| Linux | puma Debian 14 | 8.0.2-1 | [DEBIAN-CVE-2026-47736](https://patchblox.com/security/data/fix/linux/debian-cve-2026-47736.md) | Jul 18, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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