CVE-2019-15804

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2019-11-14 · updated 2026-06-17

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.

Affected products

Zyxel GS1900-10HP firmware: before 2.50\(aazi.0\)c0 — fixed in 2.50\(aazi.0\)c0
Zyxel GS1900-16 firmware: before 2.50\(aahj.0\)c0 — fixed in 2.50\(aahj.0\)c0
Zyxel GS1900-24 firmware: before 2.50\(aahl.0\)c0 — fixed in 2.50\(aahl.0\)c0
Zyxel GS1900-24E firmware: before 2.50\(aahk.0\)c0 — fixed in 2.50\(aahk.0\)c0
Zyxel Gs1900-24Hp Firmware: before 2.50\(aahm.0\)c0 — fixed in 2.50\(aahm.0\)c0
Zyxel GS1900-48 firmware: before 2.50\(aahn.0\)c0 — fixed in 2.50\(aahn.0\)c0
Zyxel Gs1900-48Hp Firmware: before 2.50\(aaho.0\)c0 — fixed in 2.50\(aaho.0\)c0
Zyxel GS1900-8 firmware: before 2.50\(aahh.0\)c0 — fixed in 2.50\(aahh.0\)c0
Zyxel GS1900-8HP firmware: before 2.50\(aahi.0\)c0 — fixed in 2.50\(aahi.0\)c0

How to fix

Upgrade to a fixed version: Zyxel GS1900-10HP firmware 2.50\(aazi.0\)c0; Zyxel GS1900-16 firmware 2.50\(aahj.0\)c0; Zyxel GS1900-24 firmware 2.50\(aahl.0\)c0; Zyxel GS1900-24E firmware 2.50\(aahk.0\)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; Zyxel GS1900-8 firmware 2.50\(aahh.0\)c0; Zyxel GS1900-8HP firmware 2.50\(aahi.0\)c0. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2019-15804 or the next vulnerability affects your stack