CVE-2023-4966 — Netscaler Application Delivery Controller

What is CVE-2023-4966?

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.

The record classifies CVE-2023-4966 under weakness classes CWE-119, NVD-CWE-noinfo. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity. 4 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 1098 days ago.

Severity and exploitation probability

CVSS v3.1 base score: 9.4 — CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
EPSS (FIRST): 99.9% probability of exploitation in the next 30 days, higher than 99.9% of all scored CVEs
CISA KEV: Listed since 2023-10-18, federal remediation deadline 2023-11-08 — used in known ransomware campaigns
Threadlinqs priority: 10/10 — CISA lists it as used in ransomware, which Threadlinqs scores at the maximum
Published: 2023-10-10, last modified 2026-07-31

Is CVE-2023-4966 being exploited?

CISA added CVE-2023-4966 to the Known Exploited Vulnerabilities catalog on 2023-10-18, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2023-11-08 under BOD 22-01. CISA flags the vulnerability as one used in known ransomware campaigns. Weaponised exploit code for CVE-2023-4966 is publicly available. 11 public proof-of-concept repositories are tracked for this identifier. A ProjectDiscovery Nuclei detection template exists (http/cves/2023/CVE-2023-4966.yaml). It currently carries a trending score of 50 in the Threadlinqs vulnerability feed.

Affected products and versions

Citrix: Netscaler Application Delivery Controller, Netscaler Gateway

Showing 2 of 4 recorded product entries.

How to fix CVE-2023-4966

The record marks a vendor fix as available for CVE-2023-4966. Patch reference: https://support.citrix.com/article/CTX579459. Vendor advisory: https://support.citrix.com/article/CTX579459. Because CVE-2023-4966 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2023-11-08. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

Threat activity tracking CVE-2023-4966

9 tracked threats in the Threadlinqs corpus reference CVE-2023-4966, either in the campaign’s CVE list or as an indicator on the campaign record.

2026 Ransomware Surge Targeting US Organizations: Identity-First Compromise, BYOVD, and Living-Off-the-Cloud Exfiltration (Qilin, Akira, Clop, INC Ransom, Play, DragonForce, Sinobi) — HIGH · 2026-08-23
LockBit 5.0 Ransomware Extortion Claim Against US Bank (U.S. Bancorp) — HIGH · 2026-08-21
Proofpoint AI Era Ransomware Report: 37% of Paying Victims Face Repeat Extortion Demands — MEDIUM · 2026-07-22
CitrixBleed-Class NetScaler ADC/Gateway SAML AuthnRequest Memory Disclosure (CVE-2026-8451) Exploited Within 24 Hours of Disclosure — CRITICAL · 2026-07-02
CitrixBleed 2.0: CVE-2026-8451 NetScaler SAML IDP Memory Overread Under Active Exploitation — CRITICAL · 2026-06-30
Kyber Ransomware: Post-Quantum Hybrid Encryption Operation Targeting Windows & VMware ESXi — CRITICAL · 2026-04-22
CitrixBleed 3 — CVE-2026-3055 & CVE-2026-4368 NetScaler ADC/Gateway Memory Overread and Session Hijack — CRITICAL · 2026-04-17
INC Ransom Affiliate Network Targeting Pacific Critical Infrastructure (AU/NZ/Tonga Joint Advisory) — CRITICAL · 2026-03-09
Citrix NetScaler Mass Reconnaissance Campaign via Residential Proxies — HIGH · 2026-02-03

Sources

Enriched from CVE.org, NVD, FIRST EPSS, CISA KEV, public proof-of-concept repositories, ProjectDiscovery Nuclei. Last verified by Threadlinqs on 2026-10-10. This product uses the NVD API but is not endorsed or certified by the NVD.

CVE-2023-4966 — Citrix Netscaler Application Delivery Controller