Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability

Zyxel GS1900 series switches contain a stack-based buffer overflow vulnerability in the CGI program which could allow a LAN-based, unauthenticated attacker to exploit the flaw and potentially execute OS commands via a crafted HTTP request.

Added to CISA’s Known Exploited Vulnerabilities catalog on 2026-09-21. Required action per CISA: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset’s internet exposure and ensuring adherence to BOD 26-04 patching guidelines. Due date: 2026-09-24.

This is an auto-synced KEV catalog record pending a full 0dayNews write-up — see CISA’s KEV catalog and the NVD record linked above for primary sources.