CVE-2019-15803

Name: CVE-2019-15803
Creator: NVD / NIST
Published: 2019-11-14T21:15:11.89+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.1/10EPSS 1.32%

Last modified Jun 17, 2026

CVE-2019-15803 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. 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. EPSS estimates a 1.32% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

9.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS Probability

1.32%

67.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-287

Affected Software

Vendor	Product	Versions
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
Zyxel	Gs1900-48hp Firmware	< 2.50\(aaho.0\)c0

References

https://jasper.la/exploring-zyxel-gs1900-firmware-with-ghidra.htmlExploit, Third Party Advisory
https://www.zyxel.com/support/gs1900-switch-vulnerabilities.shtmlVendor Advisory
https://jasper.la/exploring-zyxel-gs1900-firmware-with-ghidra.htmlExploit, Third Party Advisory
https://www.zyxel.com/support/gs1900-switch-vulnerabilities.shtmlVendor Advisory

Timeline

Published: Nov 14, 2019
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2019-15803?

How severe is CVE-2019-15803?

CVE-2019-15803 has a CVSS score of 9.1/10 (CRITICAL severity). The EPSS model estimates a 1.32% probability of exploitation in the next 30 days.

How do I fix CVE-2019-15803?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2019-15803?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST