cis-nginx-v300-2-3-3

DevOps & Security

Ensure the NGINX process ID (PID) file is secured (Manual)

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CIS 2.3.3 — Ensure the NGINX process ID (PID) file is secured

Profile Applicability

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

Description

The PID file stores the main process ID of the nginx process. This file should be protected from unauthorized modification.

Rationale

The PID file should be owned by root and the group root. It should also be readable to everyone, but only writable by root (permissions 644). This will prevent unauthorized modification of the PID file, which could cause a denial of service.

Impact

None. The PID file is managed by the master process (root). Restricting write access prevents other users from tampering with the file, but read access is generally safe and required for monitoring.

Audit Procedure

1. Identify PID File Location:

Run nginx -V and look for the --pid-path argument to confirm the location (e.g., /run/nginx.pid or /var/run/nginx.pid).

2. Verify Ownership and Permissions:

Run the following command (substituting the identified path):

stat -Lc "%U:%G %a" /run/nginx.pid

Evaluation:

Ownership: Must be root:root.
Permissions: Must be 644 (rw-r--r--) or more restrictive.

Remediation

Set the correct ownership and permissions for the PID file (replace path as needed):

chown root:root /run/nginx.pid
chmod 644       /run/nginx.pid

Default Value

The PID file is owned by root and has permissions 644 by default when building using dnf or apt.

References

https://nginx.org/en/docs/ngx_core_module.html

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	3.3 Configure Data Access Control Lists	Y	Y	Y
v7	14.6 Protect Information through Access Control Lists	Y	Y	Y

MITRE ATT&CK Mappings

Tactic	Technique
Impact	T1499 - Endpoint Denial of Service

Profile

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