---
title: "NET-FW-003 Firewall Allows Sensitive Services From Anywhere"
canonical: https://openvapt.com/checks/NET-FW-003.html
html: https://openvapt.com/checks/NET-FW-003.html
site: OpenVAPT, https://openvapt.com/
license: OpenVAPT Source-Available Licence 1.3, https://openvapt.com/legal/licence-text.html
modified: 2026-10-16
version: 0.1.0-alpha.6
---

# NET-FW-003 Firewall Allows Sensitive Services From Anywhere

Checks whether the host firewall explicitly opens a listening database, administrative or application server port to every address on the internet.

- Domain: Network
- Severity: High
- Control category: Network Exposure
- Fix effort: low
- CVSS v3.1 vector: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H`
- CIS Controls v8: 4.4
- NIST CSF 2.0: PR.IR-01
- CWE: CWE-923, CWE-1327
- OWASP Top 10 2021: A05:2021
- NIST SP 800-53 Rev. 5: SC-7, AC-4, CM-7
- Benchmark topic: Restrict firewall rules to required sources (topic only, no benchmark text)

## Why It Matters

A default-deny firewall only protects what it does not allow. A single "allow 3306 from anywhere" rule, often added while debugging, makes a database or admin panel as exposed as if there were no firewall at all.

## How It Detects

Reads the incoming allow rules of ufw (ufw status verbose), nftables (nft list ruleset, input-hook chains) or iptables (iptables -S, INPUT and ufw chains), and matches rules with no source restriction against network-reachable listening sockets on well-known data, administrative and application server ports.

## How to Fix

Delete the rule or restrict it to the addresses that need it, for example: ufw delete allow 3306 && ufw allow from 203.0.113.10 to any port 3306 proto tcp . Better, bind the service to 127.0.0.1 and reach it through an SSH tunnel or VPN.

## How to Verify

```
ufw status numbered  or  nft list ruleset  shows no rule opening that port to Anywhere.
```

## Learn the Theory

- [P3 Network Exposure and Firewalls](https://openvapt.com/academy/p3.md)
- [P12 Firewall Policy Versus What Is Listening](https://openvapt.com/academy/p12.md)

## References

- [NIST SP 800-41 Rev. 1, Guidelines on Firewalls and Firewall Policy](https://csrc.nist.gov/pubs/sp/800/41/r1/final)
- [ufw(8) manual (Ubuntu)](https://manpages.ubuntu.com/manpages/noble/man8/ufw.8.html)

## Source Code

https://github.com/OpenVAPT/openvapt/blob/574f7f3333c44b75a3c649e2d93a76d507f75adf/internal/checks/network/firewall_exposure.go

Run it: `openvapt scan --only NET-FW-003`. Read it offline: `openvapt explain NET-FW-003`.

---

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