Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability
Description
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
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.
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Details
- Vendor
- Zyxel
- Product
- Zyxel GS1900
- CVE
- CVE-2026-7273
- Affected versions
- GS1900-48HPv2 firmware 2.90: up to 2.90(ABTQ.1)C0
GS1900-8 firmware 2.90: up to 2.90(AAHH.1)C0
GS1900-8HP firmware 2.90: up to 2.90(AAHI.1)C0
GS1900-10HP firmware 2.90: up to 2.90(AAZI.1)C0
GS1900-16 firmware 2.90: up to 2.90(AAHJ.1)C0
GS1900-24 firmware 2.90: up to 2.90(AAHL.1)C0
GS1900-24E firmware 2.90: up to 2.90(AAHK.1)C0
GS1900-24EP firmware 2.90: up to 2.90(ABTO.1)C0
GS1900-24HPv2 firmware 2.90: up to 2.90(ABTP.1)C0
GS1900-48 firmware 2.90: up to 2.90(AAHN.1)C0 (from the advisory and NVD; check the exact builds in the official advisory) - CVSS score
- 8.8
- Actively exploited
- Yes, listed in the CISA Known Exploited Vulnerabilities catalog
- CISA due date
- September 24, 2026 (deadline for US federal agencies: a good benchmark for you too)
- Source
- CISA KEV – original advisory
- Published
- September 21, 2026
The description and the recommended action are quoted from the public advisory; severity, exploitation status and affected versions are compiled automatically from public sources and may contain errors. The vendor's original advisory prevails: check it before taking action. This information is provided without warranty and does not replace a professional assessment.