What is CVE-2020-28899?

CVE-2020-28899 is a critical-severity vulnerability in Zyxel Lte4506-M606, classified under Missing Authentication for Critical Function. CVSS score: 9.1/10. Published 2021-03-16.

How severe is CVE-2020-28899?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Auth bypass in Zyxel Lte4506-M606

CVE-2020-28899

The Web CGI Script on ZyXEL LTE4506-M606 V1.00(ABDO.2)C0 devices does not require authentication, which allows remote unauthenticated attackers (via crafted JSON action data to /cgi-bin/gui.cgi) to use all features provided by the router. Examples: change the router password, retrieve the Wi-Fi passphrase, send an SMS message, or modify the IP forwarding to access the internal network.

Vulnerability class: Broken Authentication

Published 2021-03-16 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.016 (75.4th percentile), scored 2026-10-03.

Low probability of exploitation in the next 30 days, but still tracked. 75th percentile — 75.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.016 · newest: 0.016 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-306 — Missing Authentication for Critical Function

References

www.zyxel.com/support/Zyxel-security-advisory-for-CGI-vulnerability-of-LTE.shtml (Vendor Advisory)

Frequently asked questions

What is CVE-2020-28899?: CVE-2020-28899 is a critical-severity vulnerability in Zyxel Lte4506-M606, classified under Missing Authentication for Critical Function. CVSS score: 9.1/10. Published 2021-03-16.
How severe is CVE-2020-28899?: Critical severity. CVSS v3 base score is 9.1 out of 10.