CISA Adds Zyxel GS1900 Series Switch Buffer Overflow to Known Exploited Vulnerabilities Catalog

The Cybersecurity and Infrastructure Security Agency (CISA) announced the addition of CVE-2026-7273 to the Known Exploited Vulnerabilities (KEV) Catalog on September 21, 2026. The vulnerability affects Zyxel GS1900 Series Switches and is classified as a stack-based buffer overflow. According to the CISA alert, there is evidence of active exploitation of this vulnerability in the wild.

CVE-2026-7273 is a stack-based buffer overflow in Zyxel GS1900 Series Switches. Stack-based buffer overflows are a frequent attack vector for malicious cyber actors and can allow remote attackers to execute arbitrary code or cause denial of service conditions. The KEV Catalog entry notes that the vulnerability poses significant risks to the federal enterprise.

Binding Operational Directive (BOD) 26-04, titled Prioritizing Security Updates Based on Risk, establishes vulnerability management requirements for Federal Civilian Executive Branch (FCEB) agencies. The directive reinforces the importance of the KEV Catalog and requires federal agencies to prioritize rapid remediation of high-risk vulnerabilities listed in the catalog on publicly exposed assets that grant total control of the asset post-exploitation. BOD 26-04 also establishes expectations for agencies to check whether threat actors had compromised the system before a patch was applied.

While BOD 26-04 applies only to FCEB agencies, CISA encourages all organizations to adopt risk-based vulnerability management and prioritize remediation of KEV Catalog vulnerabilities. CISA will continue to add vulnerabilities to the catalog that meet the specified criteria of evidence of active exploitation.

Organizations aware of an exploited vulnerability not currently listed in the KEV Catalog can submit it for potential addition through CISA's KEV Nomination Form. Potential KEV additions must have a CVE ID, evidence of exploitation, and clear mitigation guidance.