What is CVE-2021-23021?

CVE-2021-23021 is a medium-severity vulnerability in F5 nginx Controller, classified under Incorrect Permission Assignment for Critical Resource. CVSS score: 5.5/10. Published 2021-06-01.

How severe is CVE-2021-23021?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Vulnerability in F5 nginx Controller

CVE-2021-23021

The Nginx Controller 3.x before 3.7.0 agent configuration file /etc/controller-agent/agent.conf is world readable with current permission bits set to 644.

Published 2021-06-01 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.002 (12.3th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 12th percentile — 12.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000

Affected products

F5 nginx Controller
nginx Controller — versions “3.x before 3.7.0”

Weakness classification (CWE)

CWE-732 — Incorrect Permission Assignment for Critical Resource

References

support.f5.com/csp/article/K36926027 (Vendor Advisory)

Frequently asked questions

What is CVE-2021-23021?: CVE-2021-23021 is a medium-severity vulnerability in F5 nginx Controller, classified under Incorrect Permission Assignment for Critical Resource. CVSS score: 5.5/10. Published 2021-06-01.
How severe is CVE-2021-23021?: Medium severity. CVSS v3 base score is 5.5 out of 10.