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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.
KEV deadlines bind US federal agencies only, but a listing means attackers are already using the flaw, so treat it as a patch-now signal. If one of these products in your organisation was compromised, CERT-In's directions of 28 April 2022 require service providers, intermediaries, data centres, companies and government organisations to report specified incidents within 6 hours of noticing them. How to report an incident to CERT-In.
The vulnerabilities
CVE-2026-7273Federal deadline
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. CISA links: BOD 26-04 · Forensics Triage Requirements
