Exploited vulnerability · CISA KEV

Is CVE-2026-7273 exploited? Yes: in CISA KEV since 21 Sep 2026

Gociux · Zyxel GS1900 Series Switches · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2026-7273, Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 21 Sep 2026, 97 days after it was published. It affects Zyxel GS1900 Series Switches, an internet-facing product of the kind attackers use for initial access. If you run it, CISA's required action is: 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.

What it is

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.

What to do

1. Check whether you run it. Look for GS1900 Series Switches in your asset inventory, including appliances and cloud images. Stack check lists every exploited Zyxel CVE at once.
2. Apply the fix. 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.
3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 16 Jun 2026.
4. Get told next time. Email alerts when CISA adds a CVE for Zyxel.

References

• www.zyxel.com/global/en/support/security-advisories/zyxel-security-adviso
• nvd.nist.gov/vuln/detail/CVE-2026-7273

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in September 2026 · Zyxel scorecard · act-now radar.