HIGH Actively exploited CWE-121

CVE-2026-7273

Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability

Zyxel·GS1900 Series Switches

8.8/ 10

CVSS 3.1

High severity

2.7%

EPSS exploit odds

Chance of exploitation in the next 30 days

Higher than 86% of all CVEs

Listed

CISA KEV catalog

Added: Sep 21, 2026
Fix due: Sep 24, 2026
Ransomware: Not known

Timeline

Published: Jun 16, 2026
Updated: Sep 22, 2026
First covered: Sep 22, 2026
Latest story: 2 months ago

Summary

A stack-based buffer overflow vulnerability in the CGI program of Zyxel GS1900-48HPv2 firmware versions through 2.90(ABTQ.1)C0 could allow a LAN-based, unauthenticated attacker to exploit the flaw and potentially execute OS commands via a crafted HTTP request.

CWE-121Stack-based buffer overflow

Attack profile

Attack vectorAdjacent

ComplexityLow

PrivilegesNone

User interactionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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.

Affected products

Zyxel GS1900-48HPv2 firmware<= 2.90(ABTQ.1)C0
Zyxel GS1900-8 firmware<= 2.90(AAHH.1)C0
Zyxel GS1900-8HP firmware<= 2.90(AAHI.1)C0
Zyxel GS1900-10HP firmware<= 2.90(AAZI.1)C0
Zyxel GS1900-16 firmware<= 2.90(AAHJ.1)C0
Zyxel GS1900-24 firmware<= 2.90(AAHL.1)C0
Zyxel GS1900-24E firmware<= 2.90(AAHK.1)C0
Zyxel GS1900-24EP firmware<= 2.90(ABTO.1)C0

References

CVE.org recordcve.org NVD entrynvd.nist.gov CISA KEV listingcisa.gov Vendor advisoryzyxel.com