CVE entry · CVE-2026-7273
CVE-2026-7273: Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability
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.
- Actively exploited: added to CISA’s KEV catalog on September 21, 2026.
- Use by ransomware: not established so far.
- Remediation deadline for US federal agencies: September 24, 2026.
Description from CISA’s KEV catalog.
What to do
- Check whether your estate includes Zyxel GS1900 Series Switches, including internet-facing devices.
- Apply the vendor’s patch or mitigations (references below). Failing that, isolate the product or stop using it, as CISA requires of US federal agencies.
- An exploited vulnerability has often been used before it was fixed: look for signs of compromise, especially on internet-facing devices.