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Citrix NetScaler vulnerability (CVE-2026-88779) in active exploitation

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Written by Sophos Counter Threat Unit Research Team

Citrix NetScaler (CVE-2026-88779) feature image
Threat ResearchadvisoryvulnerabilityCitrix

On October 4, 2026, Citrix disclosed a high-severity (CVSS score of 8.7) memory overflow vulnerability (CVE-2026-88779) affecting Citrix NetScaler ADC and Citrix NetScaler Gateway deployments that are configured as either a SAML Service Provider (SP) or SAML Identity Provider (IdP). Successful exploitation can cause a denial of service (DoS) condition, potentially disrupting authentication services and remote access functionality. This vulnerability affects customer-managed Citrix NetScaler ADC and NetScaler Gateway appliances. Citrix-managed cloud services and Citrix-managed Adaptive Authentication services are not affected, as the required updates are applied to those platforms.

Active exploitation has been reported. Citrix has observed targeted attacks against unpatched NetScaler deployments, and the U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added CVE-2026-88779 to its Known Exploited Vulnerabilities (KEV) Catalog.

Recommended actions

Counter Threat Unitâ„¢ (CTU) researchers recommend that organizations identify affected systems and apply the latest Citrix security updates as soon as possible as appropriate to minimize the risk of service disruption. Organizations should prioritize internet-facing and business-critical deployments.

Sophos countermeasures

SophosLabs continues to monitor the threat landscape for activity related to this vulnerability and will deliver detections and protections as available.

About the Author(s)

Author - Sophos Logo

Sophos Counter Threat Unit Research Team

Sophos Counter Threat Unit™ (CTU) researchers are recognized authorities in the cybersecurity field, regularly contributing expert analysis to global media, publishing technical analyses for the security community, and presenting about emerging threats at leading security conferences. Backed by Sophos’ advanced security technologies and a broad network of intelligence contacts and partners, the CTU™ plays a critical role in identifying and tracking threat actors and analyzing anomalous activity, uncovering new attack techniques, threats, and major shifts in the threat landscape.