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CVE-2019-15803

9.1 · CRITICAL

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0.

Published Nov 14, 2019CWE-287EPSS 1.32%

Overview

CVE-2019-15803 is a critical-severity vulnerability. It was published on November 14, 2019 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. Through an undocumented sequence of keypresses, undocumented functionality is triggered. A diagnostics shell is triggered via CTRL-ALT-t, which prompts for the password returned by fds_sys_passDebugPasswd_ret(). The firmware contains access control checks that determine if remote users are allowed to access this functionality. The function that performs this check (fds_sys_remoteDebugEnable_ret in libfds.so) always return TRUE with no actual checks performed. The diagnostics menu allows for reading/writing arbitrary registers and various other configuration parameters which are believed to be related to the network interface chips.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refjasper.la/exploring-zyxel-gs1900-firmware-with-ghidra.htmlRefwww.zyxel.com/support/gs1900-switch-vulnerabilities.shtmlRefjasper.la/exploring-zyxel-gs1900-firmware-with-ghidra.htmlRefwww.zyxel.com/support/gs1900-switch-vulnerabilities.shtml

How CyberStrike helps

Frequently asked questions

What is CVE-2019-15803?

CVE-2019-15803 is a critical-severity vulnerability. It was published on November 14, 2019 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2019-15803?

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2019-15803?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2019-15803?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2019-15803 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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