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CISA KEV source record / CVE-2023-4966

Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow Vulnerability

Citrix / NetScaler ADC and NetScaler Gateway

Known exploitation catalogNot a Secureline discoveryNot a live alert

Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow vulnerability that allows for sensitive information disclosure when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.

CVE identifier
CVE-2023-4966
Added to KEV
Oct 18, 2023
CISA catalog dueDate
Nov 8, 2023

The dates above are catalog fields. The addition date does not establish when the vulnerability was discovered or first exploited. Confirm which requirements apply to your organisation separately.

Publisher's required action

Apply mitigations and kill all active and persistent sessions per vendor instructions [https://www.netscaler.com/blog/news/cve-2023-4966-critical-security-update-now-available-for-netscaler-adc-and-netscaler-gateway/] OR discontinue use of the product if mitigations are unavailable.

This wording is attributed to the CISA snapshot. Verify current vendor guidance, affected versions and your deployment before applying changes.

Keep the signals separate.

Ransomware use, as reported by CISA
Known
CVSS severity
Not supplied by KEV
EPSS probability
Not available

No EPSS value was supplied for this record in the current snapshot. Unknown values are not treated as zero.

“Unknown” ransomware use is an unknown source field, not proof that ransomware activity has not occurred.

Source notes

https://www.netscaler.com/blog/news/cve-2023-4966-critical-security-update-now-available-for-netscaler-adc-and-netscaler-gateway/, https://support.citrix.com/article/CTX579459/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve20234966-and-cve20234967 ; https://nvd.nist.gov/vuln/detail/CVE-2023-4966

Source & freshness

Catalog version 2026.11.06
Source updated: Nov 6, 2026, 7:44 PM UTC
Successfully checked: Nov 7, 2026, 6:22 PM UTC
CISA source snapshot ↗CVE record ↗EPSS methodology ↗

Automated source record, not an editorial advisory or an independent discovery. No affected or fixed version is inferred, and no organisation-specific risk rating is generated.