Zyxel GS1900 Series Switches' CGI Program Stack-Based Buffer Overflow Allows a LAN-Side Unauthenticated Attacker to Execute OS Commands via Crafted HTTP Requests; CISA's September 24th KEV Deadline Has Passed

Last refreshed2026-09-27

Status: KEV | Advisory ID: CVE-2026-7273

Key Details

CVE	CVE-2026-7273
Vulnerability Name	Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability
Affected products	Zyxel GS1900 Series Switches
Exploitation status	Listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating confirmed active exploitation.
Classified as	CWE-121 (Stack-based Buffer Overflow)
KEV listing	Added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2026-09-21.
Exploitation prediction (EPSS)	2.50% probability of exploitation in the next 30 days (84% percentile) -- FIRST.org's EPSS model.
Federal remediation deadline	2026-09-24 (CISA KEV, Binding Operational Directive).

Affected Products, Subsystems & Sectors

Vendor	Product	Affected Versions	Patch Status
Zyxel	GS1900 Series Switches

Vendor

Product

Affected Versions

Patch Status

Zyxel

GS1900 Series Switches

Subsystems	Industrial Network - Switches
Sectors	Multiple

What to Know

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

Monitor Zyxel's web page for any future patch releases.

References

Source	Reference
NVD	https://nvd.nist.gov/vuln/detail/CVE-2026-7273
CVE	https://www.cve.org/CVERecord?id=CVE-2026-7273

Source

Reference

NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-7273

CVE

https://www.cve.org/CVERecord?id=CVE-2026-7273

KEV Required Action

Field	Value
KEV Link	https://www.cisa.gov/known-exploited-vulnerabilities-catalog
Date Added to KEV	2026-09-21
Required Action Due Date	2026-09-24
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.

Field

Value

KEV Link

https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Date Added to KEV

2026-09-21

Required Action Due Date

2026-09-24

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.