What’s Vulnerable › Vulnerabilities

CVE-2019-15800

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 3.9% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2019-11-14 · updated 2026-06-17
• Weakness: CWE-78

Description

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. Due to lack of input validation in the cmd_sys_traceroute_exec(), cmd_sys_arp_clear(), and cmd_sys_ping_exec() functions in the libclicmd.so library contained in the firmware, an attacker could leverage these functions to call system() and execute arbitrary commands on the switches. (Note that these functions are currently not called in this version of the firmware, however an attacker could use other vulnerabilities to finally use these vulnerabilities to gain code execution.)

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

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