---
title: "NET-FW-002 IPv6 Listeners Without IPv6 Firewall"
canonical: https://openvapt.com/checks/NET-FW-002.html
html: https://openvapt.com/checks/NET-FW-002.html
site: OpenVAPT, https://openvapt.com/
license: OpenVAPT Source-Available Licence 1.3, https://openvapt.com/legal/licence-text.html
modified: 2026-10-14
version: 0.1.0-alpha.6
---

# NET-FW-002 IPv6 Listeners Without IPv6 Firewall

Network-reachable IPv6 listeners exist without a default-deny IPv6 firewall policy.

- Domain: Network
- Severity: High
- Control category: Network Exposure
- Fix effort: medium
- 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
- NIST SP 800-53 Rev. 5: SC-7

## Why It Matters

An IPv4-only firewall does not protect IPv6 services, creating an alternate path that bypasses intended filtering.

## How It Detects

Parses /proc/net/tcp6 and udp6, then inspects nft list ruleset and ip6tables -S for an input drop or reject policy.

## How to Fix

Apply equivalent default-deny filtering for IPv6 with nftables or ip6tables and explicitly allow required services. Caution: allow SSH and ICMPv6 neighbour discovery and router messages before applying the default deny, or remote IPv6 sessions and IPv6 connectivity are cut.

## How to Verify

```
Run ip6tables -S and nft list ruleset, then confirm the input chain has a default drop or reject policy.
```

## Learn the Theory

- [P3 Network Exposure and Firewalls](https://openvapt.com/academy/p3.md)

## References

- [NIST SP 800-119, Guidelines for the Secure Deployment of IPv6](https://csrc.nist.gov/pubs/sp/800/119/final)

## Source Code

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

Run it: `openvapt scan --only NET-FW-002`. Read it offline: `openvapt explain NET-FW-002`.

---

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