The Cybersecurity and Infrastructure Security Agency (CISA) released a Cybersecurity Advisory (CSA), Threat Actors Exploiting Citrix CVE-2023-3519 to Implant Webshells, to warn organizations about threat actors exploiting CVE-2023-3519, an unauthenticated remote code execution (RCE) vulnerability affecting NetScaler (formerly Citrix) Application Delivery Controller (ADC) and NetScaler Gateway. In June 2023, threat actors exploited this vulnerability as a zero-day to drop a webshell on a critical infrastructure organization’s NetScaler ADC appliance. The webshell enabled the actors to perform discovery on the victim’s active directory (AD) and collect and exfiltrate AD data. The actors attempted to move laterally to a domain controller but network-segmentation controls for the appliance blocked movement.
This CSA details tactics, techniques, and procedures (TTPs) shared with CISA by the victim.
If activity is detected, CISA strongly urges all critical infrastructure organizations follow the recommendations found within this advisory, such as prioritizing patching known exploited vulnerabilities like Citrix CVE-2023-3519.