What is CVE-2021-23020?

CVE-2021-23020 is a medium-severity vulnerability in F5 nginx Controller, classified under Use of Insufficiently Random Values. CVSS score: 5.5/10. Published 2021-06-01.

How severe is CVE-2021-23020?

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

Vulnerability in F5 nginx Controller

CVE-2021-23020

The NAAS 3.x before 3.10.0 API keys were generated using an insecure pseudo-random string and hashing algorithm which could lead to predictable keys.

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: 0.003 (15.4th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 15th percentile — 15.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000

Affected products

F5 nginx Controller
nginx Controller — versions “3.x before 3.10.0”

Weakness classification (CWE)

CWE-330 — Use of Insufficiently Random Values

References

support.f5.com/csp/article/K45263486 (Vendor Advisory)

Frequently asked questions

What is CVE-2021-23020?: CVE-2021-23020 is a medium-severity vulnerability in F5 nginx Controller, classified under Use of Insufficiently Random Values. CVSS score: 5.5/10. Published 2021-06-01.
How severe is CVE-2021-23020?: Medium severity. CVSS v3 base score is 5.5 out of 10.