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Vulnerability record · CVE-2019-15804 · published 14 November 2019

CVE-2019-15804: Zyxel gs1900-8 firmware vulnerability

Zyxel · Gs1900 8 Firmware

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. By sending a signal to the CLI process, undocumented functionality is triggered. Specifically, a menu can be triggered by sending the SIGQUIT signal to the CLI application (e.g., through CTRL+\ via SSH). The access control check for this menu does work and prohibits accessing the menu, which contains "Password recovery for specific user" options. The menu is believed to be accessible using a serial console.

7.5 CVSS 3.1 High EPSS 0.93% · top 40.5%
7.5CVSS 3.1 base score, v2 5.0
0.93%EPSS exploitation probability, 30 days
NoNot in CISA KEV
9Affected product versions listed by NVD
4References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. By sending a signal to the CLI process, undocumented functionality is triggered. Specifically, a menu can be triggered by sending the SIGQUIT signal to the CLI application (e.g., through CTRL+\ via SSH). The access control check for this menu does work and prohibits accessing the menu, which contains "Password recovery for specific user" options. The menu is believed to be accessible using a serial console.

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

Affected products

9 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://jasper.la/exploring-zyxel-gs1900-firmware-with-ghidra.html ExploitThird Party Advisory
https://www.zyxel.com/support/gs1900-switch-vulnerabilities.shtml Vendor Advisory
https://jasper.la/exploring-zyxel-gs1900-firmware-with-ghidra.html ExploitThird Party Advisory
https://www.zyxel.com/support/gs1900-switch-vulnerabilities.shtml Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2019-15804), CISA KEV, FIRST EPSS (scores of 2026-10-10). This page is refreshed as NVD updates the record.