CVE-2019-15803

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering.

Exploit odds

1.3% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2019-11-14 21:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 02:21 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.3% in the next 30 days (EPSS).
• Severity: 9.1 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2019-11-14 21:15 UTC

Last modified

2026-06-17 02:21 UTC

Exploit probability

1.3% · EPSS, next 30 days

Weakness

CWE-287 · Improper authentication

Record status

Modified

Affected

• Zyxel gs1900-8 Firmware < 2.50\(aahh.0\)c0
• Zyxel gs1900-8hp Firmware < 2.50\(aahi.0\)c0
• Zyxel gs1900-10hp Firmware < 2.50\(aazi.0\)c0
• Zyxel gs1900-16 Firmware < 2.50\(aahj.0\)c0
• Zyxel gs1900-24e Firmware < 2.50\(aahk.0\)c0
• Zyxel gs1900-24 Firmware < 2.50\(aahl.0\)c0
• Zyxel gs1900-24hp Firmware < 2.50\(aahm.0\)c0
• Zyxel gs1900-48 Firmware < 2.50\(aahn.0\)c0

Attack profile CVSS 3.1 · 9.1

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

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