What’s Vulnerable › Vulnerabilities

CVE-2019-15799

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2019-11-14 · updated 2026-06-17
• Weakness: CWE-269

Description

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. User accounts created through the web interface of the device, when given non-admin level privileges, have the same level of privileged access as administrators when connecting to the device via SSH (while their permissions via the web interface are in fact restricted). This allows normal users to obtain the administrative password by running the tech-support command via the CLI: this contains the encrypted passwords for all users on the device. As these passwords are encrypted using well-known and static parameters, they can be decrypted and the original passwords (including the administrator password) can be obtained.

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

• https://jasper.la/exploring-zyxel-gs1900-firmware-with-ghidra.html
• https://vimeo.com/354726424
• https://www.zyxel.com/support/gs1900-switch-vulnerabilities.shtml
• https://jasper.la/exploring-zyxel-gs1900-firmware-with-ghidra.html
• https://vimeo.com/354726424
• https://www.zyxel.com/support/gs1900-switch-vulnerabilities.shtml

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