CVE-2026-7273: in the CISA KEV catalogue
Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability. CISA added CVE-2026-7273 to the Known Exploited Vulnerabilities catalogue on 2026-09-21 with a default due date of 2026-09-24. Known ransomware campaign use: Unknown. Forensic triage flag: Yes.
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. (CISA description)
- Vendor / product
- Zyxel GS1900 Series Switches
- CWE
- CWE-121
- CISA 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.
- EPSS
- 2.8%, percentile 86 (scored 2026-11-03)
EPSS puts about 2.8 in 100 odds (2.8%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 86% of scored CVEs. This is a model estimate about exploitation anywhere, not about your environment.
Vendor and reference links (from CISA)
- https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-stack-based-buffer-overflow-vulnerability-in-gs1900-series-switches-06-16-2026
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk
- https://nvd.nist.gov/vuln/detail/CVE-2026-7273
Your own deadline under CISA BOD 26-04 depends on exposure, automatability and technical impact: work it out with the BOD 26-04 calculator.
Frequently asked questions
Is CVE-2026-7273 in the CISA KEV catalogue?
Yes. CISA added CVE-2026-7273 (Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2026-09-21. CISA's default due date for it is 2026-09-24.
Is CVE-2026-7273 used in ransomware attacks?
CISA marks known ransomware campaign use as Unknown for CVE-2026-7273. That means CISA lacks confirmation, not that ransomware groups do not use it.
What should I do about CVE-2026-7273?
CISA's 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.
Sources
- CISA, Known Exploited Vulnerabilities Catalog (accessed 2026-11-03)
- FIRST, Exploit Prediction Scoring System (EPSS) (EPSS by FIRST; scores generated by Empirical Security)
- NVD record for CVE-2026-7273