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Fencer Intel
critical 9.4

CVE-2023-4966 kev+ ransomware in the critical feed json

Unauthenticated sensitive information disclosure

published 3y ago modified 3mo ago also EUVD-2023-54802

cvss
9.4
version 3.1, CNA
cisa kev
Exploited
added 2023-10-18, used in ransomware
epss
100.0%
EPSS 100.0% chance of exploitation in 30 days, percentile 99.9%
public exploits
1
Metasploit

Summary

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.

Patch / fix

cisa 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.

  • Citrix NetScaler ADC 8.50, 37.164, 49.15, 55.300, 92.19
  • Citrix NetScaler Gateway 8.50, 49.15, 92.19

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Timeline

  1. CISA SSVC: exploitation active
  2. Published
  3. Added to CISA KEV
  4. First public exploit (Metasploit auxiliary/scanner/http/citrix_bleed_cve_2023_4966)
  5. CISA patch deadline

Known exploited

Added
3y ago
Patch by
2023-11-08 (3y ago)
Ransomware
Known to be used in ransomware campaigns
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.
Vendor, product
Citrix, NetScaler ADC and NetScaler Gateway
CISA name
Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow Vulnerability

Ransomware

Groups reported to have exploited it in intrusions.

  • LockBit ransomware gang
  • Medusa ransomware gang
  • BlackCat ransomware gang
  • INC Ransom ransomware gang
  • Storm-0501 affiliate

reported by doublepulsar.combleepingcomputer.comtherecord.mediasecureworks.commicrosoft.com

Ransomware Vulnerability Matrix by BushidoUK (github.com/BushidoUK/Ransomware-Vulnerability-Matrix), reformatted per CVE. CC BY 4.0

ATT&CK techniques

How it is exploited and what it leads to, in MITRE ATT&CK terms.

  • T1574 Hijack Execution Flow exploitation
  • T1005 Data from Local System primary impact
  • T1134.001 Token Impersonation/Theft secondary impact

kev release 2025-07-28, att&ck v16.1. KEV to ATT&CK mappings by the MITRE Center for Threat-Informed Defense (Mappings Explorer, Apache-2.0). © 2026 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation. Terms of use

CISA SSVC

Exploitation
Active, exploited in the wild
Automatable
yes
Technical impact
total
Assessed
3y ago

Exploit prediction

100.00% chance of exploitation in the next 30 days, higher than 99.9% of all scored CVEs (FIRST EPSS, 2026-11-14).

Exploits and checks

CVSS scores

assigned by version score vector
CNA 3.1 9.4 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected products

  • Citrix NetScaler ADC
  • Citrix NetScaler Gateway

Classification

Weakness
  • CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.