CVE-2026-7273: Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability

High severity, CVSS 8.8. Actively exploited: in CISA KEV since 2026-09-21. EPSS: 2.5% chance of exploitation in the next 30 days.

A stack-based buffer overflow vulnerability in the CGI program of Zyxel GS1900-48HPv2 firmware versions through 2.90(ABTQ.1)C0 could allow a LAN-based, unauthenticated attacker to exploit the flaw and potentially execute OS commands via a crafted HTTP request.

Affected products

• Zyxel GS1900-10hp Firmware: before 2.90\(aazi.2\)c0 (fixed in 2.90\(aazi.2\)c0)
• Zyxel GS1900-16 Firmware: before 2.90\(aahj.2\)c0 (fixed in 2.90\(aahj.2\)c0)
• Zyxel GS1900-24 Firmware: before 2.90\(aahl.2\)c0 (fixed in 2.90\(aahl.2\)c0)
• Zyxel GS1900-24e Firmware: before 2.90\(aahk.2\)c0 (fixed in 2.90\(aahk.2\)c0)
• Zyxel GS1900-24ep Firmware: before 2.90\(abto.2\)c0 (fixed in 2.90\(abto.2\)c0)
• Zyxel GS1900-24hpv2 Firmware: before 2.90\(abtp.2\)c0 (fixed in 2.90\(abtp.2\)c0)
• Zyxel GS1900-48 Firmware: before 2.90\(aahn.2\)c0 (fixed in 2.90\(aahn.2\)c0)
• Zyxel GS1900-48hpv2 Firmware: before 2.90\(abtq.2\)c0 (fixed in 2.90\(abtq.2\)c0)
• Zyxel GS1900-8 Firmware: before 2.90\(aahh.2\)c0 (fixed in 2.90\(aahh.2\)c0)
• Zyxel GS1900-8hp Firmware: before 2.90\(aahi.2\)c0 (fixed in 2.90\(aahi.2\)c0)

Published 2026-06-16. Last modified 2026-09-22.