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Citrix · NetScaler ADC and NetScaler Gateway

CVE-2023-4966

Unauthenticated sensitive information disclosure

Exploited in attacks Used by ransomware Critical 9.4 Attack chance: >99.9%
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What it is

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.

CISA: 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.

What to do

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.

Deadline for US federal agencies: November 8, 2023

Added to the CISA list
October 18, 2023
Published
October 10, 2023
Severity
Critical 9.4 CVSS 3.1
Chance of attacks in the next 30 days (EPSS)
>99.9% in the top 0.1% of all known vulnerabilities
Weakness
CWE-119
More details
NVD · CVE.org · CISA
All references (2)

More exploited flaws from Citrix

AddedVulnerabilityProductSeverityAttack chance
Aug 26, 2026Improper Restriction of Operations within the Bounds of a Memory BufferCVE-2026-8452NetScaler ADC and NetScaler GatewayHigh 8.81.0%
Jan 17, 2024Code InjectionCVE-2023-6548NetScaler ADC and NetScaler GatewayMedium 5.53.2%
Jan 17, 2024Buffer OverflowCVE-2023-6549NetScaler ADC and NetScaler GatewayHigh 8.258%
Jul 19, 2023Code InjectionCVE-2023-3519used by ransomwareNetScaler ADC and NetScaler GatewayCritical 9.899.7%
Oct 4, 2026Improper Restriction of Operations within the Bounds of a Memory BufferCVE-2026-88779NetScalerHigh 8.711%
Sep 27, 2026Improper Input ValidationCVE-2026-88771NetScalerCritical 9.582%
Sep 27, 2026Improper Restriction of Operations within the Bounds of a Memory BufferCVE-2026-88772NetScalerCritical 9.578%
Sep 9, 2026Authentication Bypass Using an Alternate Path or ChannelCVE-2026-19490NetScalerCritical 9.333%

All of them →

Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.