CVE-2019-15801: Zyxel GS1900-10hp Firmware

High severity, CVSS 7.5. EPSS: 1.5% chance of exploitation in the next 30 days.

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. The firmware image contains encrypted passwords that are used to authenticate users wishing to access a diagnostics or password-recovery menu. Using the hardcoded cryptographic key found elsewhere in the firmware, these passwords can be decrypted. This is related to fds_sys_passDebugPasswd_ret() and fds_sys_passRecoveryPasswd_ret() in libfds.so.0.0.

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.