Threat Intelligence / CVE / CVE-2023-4966

CVE-2023-4966 — Citrix Netscaler Application Delivery Controller

CISA KEVRansomware
CVSS v3.1 9.4 (CRITICAL) · EPSS 94.3% (higher than 99.9% of all scored CVEs) · Priority 10/10 · Published 2023-10-10

As of 2025-10-24, CVE-2023-4966 is a CRITICAL-severity vulnerability in Citrix Netscaler Application Delivery Controller, CVSS v3.1 9.4, EPSS 94.3% (99.9th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2023-10-18), with a US federal remediation deadline of 2023-11-08, and CISA links it to known ransomware campaigns. Threadlinqs Intelligence links 7 tracked threat campaigns to CVE-2023-4966, most recently “2026 Ransomware Surge Targeting US Organizations: Identity-First Compromise, BYOVD, and Living-Off-the-Cloud Exfiltration (Qilin, Akira, Clop, INC Ransom, Play, DragonForce, Sinobi)”.

Last updated: 2025-10-24

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 1068 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)
94.3% 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 2025-10-24

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. It currently carries a trending score of 40 in the Threadlinqs vulnerability feed.

Affected products and versions

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

7 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.

Sources

Seeded from nvd and not yet processed by the Threadlinqs enrichment pipeline, so blank CVSS, EPSS or KEV fields above mean NOT MEASURED rather than measured-absent.

Full detection coverage & IOCs for threats exploiting CVE-2023-4966 are available via the Threadlinqs MCP server (Purple tier). View plans →

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