# Cis Nginx V300 4 1 6

> Ensure awareness of TLS 1.3 new Diffie-Hellman parameters (Manual)

- Skill: `cyberstrikeus/cis-nginx-v300-4-1-6` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-nginx-v300-4-1-6`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-nginx-v300-4-1-6/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/cis-nginx-v300-4-1-6

---


# CIS 4.1.6 — Ensure awareness of TLS 1.3 new Diffie-Hellman parameters

## Profile Applicability

- Level 1 - Webserver
- Level 1 - Proxy
- Level 1 - Loadbalancer

## Description

This control is not applicable to environments exclusively using TLS 1.3.

## Rationale

The TLS 1.3 protocol (RFC 8446) deprecates the use of custom finite-field Diffie-Hellman (DHE) groups, which were configured via the `ssl_dhparam` directive in NGINX. Instead, TLS 1.3 exclusively uses a set of pre-defined, standardized, and secure elliptic curve (ECDHE) and finite-field (FFDHE) groups for its key exchange mechanism. This design eliminates the risk associated with weak or misconfigured custom DH parameters. As such, the `ssl_dhparam` directive has no effect in a TLS 1.3-only configuration.

## Impact

None for a TLS 1.3-only configuration.

## Audit Procedure

Verify that the configuration does not rely on TLS 1.2 **or older protocols** that would require this setting. This control is implicitly passed if control 4.1.4 ("Ensure only modern TLS protocols are used") is configured for TLS 1.3 exclusively.

## Remediation

No remediation is necessary. Ensure `ssl_protocols TLSv1.3;` is set. The `ssl_dhparam` directive should be removed as it is obsolete.

## Default Value

Not applicable for TLS 1.3-only configurations.

## References

1. https://datatracker.ietf.org/doc/html/rfc8446#page-95
2. https://nginx.org/en/docs/http/ngx_http_ssl_module.html#ssl_dhparam

## CIS Controls

| Controls Version | Control                                           | IG 1 | IG 2 | IG 3 |
| ---------------- | ------------------------------------------------- | ---- | ---- | ---- |
| v8               | 3.10 Encrypt Sensitive Data in Transit            | N    | Y    | Y    |
| v7               | 14.4 Encrypt All Sensitive Information in Transit | N    | Y    | Y    |

## MITRE ATT&CK Mappings

| Tactic            | Technique                       |
| ----------------- | ------------------------------- |
| Credential Access | T1557 - Adversary-in-the-Middle |

## Profile

- Level 1 - Webserver
- Level 1 - Proxy
- Level 1 - Loadbalancer