CVE-2023-4966
Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow Vulnerability
Citrix NetScaler ADC and NetScaler Gateway
Sensitive information disclosure in NetScaler ADC and NetScaler Gateway when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 18 October 2023. US federal agencies were required to remediate it by 8 November 2023. CISA records this vulnerability as known to be used in ransomware campaigns.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 100%, which is higher than 99.9% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Frequently asked questions
Is CVE-2023-4966 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2023-4966.
What does CVE-2023-4966 affect?
CVE-2023-4966 affects Citrix NetScaler ADC and NetScaler Gateway. Sensitive information disclosure in NetScaler ADC and NetScaler Gateway when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.
How severe is CVE-2023-4966?
CVE-2023-4966 is rated CRITICAL with a CVSS base score of 9.4. EPSS puts the probability of exploitation in the next 30 days at 100%, higher than 99.9% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 8 November 2023.
How should organisations respond to CVE-2023-4966?
Apply the vendor patch for Citrix NetScaler ADC and NetScaler Gateway as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.