How severe is CVE-2020-28899?

CVE-2020-28899 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2020-28899 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (73rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-28899?

CVE-2020-28899 primarily affects Zyxel Lte4506-m606 Firmware. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-28899?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2020-28899 published?

CVE-2020-28899 was published on 2021-03-16 and last updated on 2026-06-17.

CVE-2020-28899

CVE-2020-28899 is a critical-severity vulnerability in Zyxel Lte4506-m606 Firmware with a CVSS 3.x base score of 9.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-306.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
CVSS v2: 6.4
EPSS exploit prediction: 2% (73rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-306
Affected product: Zyxel Lte4506-m606 Firmware
Published: 2021-03-16
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is 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.
How severe is CVE-2020-28899?: CVE-2020-28899 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2020-28899 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (73rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-28899?: CVE-2020-28899 primarily affects Zyxel Lte4506-m606 Firmware. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-28899?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2020-28899 published?: CVE-2020-28899 was published on 2021-03-16 and last updated on 2026-06-17.

References

https://www.zyxel.com/support/Zyxel-security-advisory-for-CGI-vulnerability-of-LTE.shtml

Affected products (3)

cpe:2.3:o:zyxel:lte4506-m606_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:lte7460-m608_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:wah7706_firmware:*:*:*:*:*:*:*:*

Other CWE-306 (Missing Authentication for Critical Function) vulnerabilities

CVE-2026-54309 — Critical (CVSS 10.0): n8n is an open source workflow automation platform. Prior to 2.25.7 and 2.26.2, when @n8n/mcp-browser is run in HTTP…
CVE-2026-50242 — Critical (CVSS 10.0): In JetBrains Hub before 2026.1.13757, 2025.3.148033, 2025.2.148048, 2025.1.148120, 2024.3.148430, 2024.2.148429…
CVE-2026-49257 — Critical (CVSS 10.0): mcp-pinot is a Python-based Model Context Protocol (MCP) server for interacting with Apache Pinot. In versions 3.0.1…
CVE-2026-46846 — Critical (CVSS 10.0): Vulnerability in the Oracle WebCenter Portal product of Oracle Fusion Middleware (component: Security Framework).…
CVE-2026-46803 — Critical (CVSS 10.0): Vulnerability in the Oracle WebCenter Portal product of Oracle Fusion Middleware (component: Security Framework).…
CVE-2026-46800 — Critical (CVSS 10.0): Vulnerability in the Oracle WebCenter Sites product of Oracle Fusion Middleware (component: WebCenter Sites).…

Browse all CWE-306 (Missing Authentication for Critical Function) vulnerabilities →