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CISA KEV 21 Sep 2026: 1 exploited flaw in Zyxel

1 vulnerability
Conceptual illustration: An enterprise router and firewall appliance, shielded network ports and a precise glowing patch plate. Headline: NETWORK SECURITY.

AI-generated illustration by CyberShitty. Not a photograph or a document from the organisations named.

On 21 September 2026, CISA added 1 actively exploited vulnerability affecting Zyxel to its Known Exploited Vulnerabilities catalog. If you run any of these products, patch or mitigate now — exploitation is already happening.

CVE-2026-7273Federal deadline

In this section

Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability

Zyxel / GS1900 Series Switches / CWE-121

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.

Required action: 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.