CVE-2019-15804: Zyxel GS1900-10hp Firmware

High severity, CVSS 7.5. EPSS: 0.9% chance of exploitation in the next 30 days.

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)

Published 2019-11-14. Last modified 2026-06-17.