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

> Attackers can spoof source IP addresses by injecting repeated PROXY protocol headers on persistent connections in Puma web server.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Jul 2026
- **Updated:** 15 Jul 2026
- **Also known as:** CLEANSTART-2026-CK66622, CLEANSTART-2026-OT47586, DEBIAN-CVE-2026-47737, GHSA-2vqw-3mp8-cgmx, MINI-24x8-c52w-83cr, MINI-3pfv-c45h-h6h3, MINI-66p5-wfq8-jc5q, MINI-67fc-wfr4-2ppp, MINI-736w-qcgc-5f36, MINI-77h6-p8j8-2w43, MINI-7vm2-fhh9-q9c3, MINI-922m-3w3m-jpr8, MINI-9fj5-h78h-8627, MINI-fwf2-9wx9-p4w4, MINI-g23f-x647-4q9g, MINI-gc67-qhr3-4cgm, MINI-gp4r-2wh8-2vpv, MINI-h9hj-cp8p-gfh3, MINI-hgph-vrgh-gfcx, MINI-jc4r-rj55-jp67, MINI-jj3w-wq3c-pxmj, MINI-mwhw-83m9-wg37, MINI-qfmp-862p-58mp, MINI-qhhh-c3rv-hfh9, MINI-qr22-xqx2-hfm7, MINI-qw54-p44g-3fcp, MINI-r35w-mhfq-94vm, MINI-rwpv-x32m-4r46, MINI-vq7f-xg9c-v2jq, MINI-w64m-7f3v-mmv3, UBUNTU-CVE-2026-47737

## What is CVE-2026-47737?

CVE-2026-47737 is a high-severity vulnerability in puma, published on 14 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-345 (Insufficient Verification of Data Authenticity), CWE-290 (Authentication Bypass by Spoofing)

## Which versions are affected by CVE-2026-47737?

4 open source packages ship an affected version, including puma.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `puma` | RubyGems | From 5.5.0 | 7.2.1 |
| `puma` | RubyGems | From 5.5.0 | 7.2.1 |
| `puma` | RubyGems | From 8.0.0 | 8.0.2 |
| `puma` | RubyGems | From 8.0.0 | 8.0.2 |

## How do I fix CVE-2026-47737?

Upgrade puma to a fixed version for your release line: 7.2.1 or 8.0.2.

## Is CVE-2026-47737 being exploited?

There is no known exploitation of CVE-2026-47737 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-47737 and fix it if it is affected.

What it is: CVE-2026-47737 is a high-severity vulnerability in puma, published on 14 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-47737 in the wild and no public exploit code.

Affected packages and fixed versions:
- puma (RubyGems): affected from 5.5.0; fixed in 7.2.1
- puma (RubyGems): affected from 5.5.0; fixed in 7.2.1
- puma (RubyGems): affected from 8.0.0; fixed in 8.0.2
- puma (RubyGems): affected from 8.0.0; fixed in 8.0.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-47737/ (Markdown: https://insights.sbomify.com/CVE-2026-47737/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-47737
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-47737
- OSV: https://osv.dev/vulnerability/CVE-2026-47737

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-47737/
Summaries are generated and may contain mistakes; the official description above is the record.