New Citrix NetScaler Zero-Day (CVE-2026-88779) Actively Exploited, Leading to Denial of Service

Citrix NetScaler administrators are addressing a new high-severity zero-day vulnerability, CVE-2026-88779, which is being actively exploited in targeted attacks. The memory overflow flaw impacts NetScaler ADC and Gateway instances configured as a SAML SP or IdP, potentially resulting in denial-of-service. This discovery follows closely after two other exploited zero-days were patched. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added this CVE to its Known Exploited Vulnerabilities catalog.