What is the CVSS score of CVE-2023-4966?

CVE-2023-4966 has a CVSS 3.1 base score of 9.4 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L. EPSS exploitation probability: 94.3%.

Which versions of NetScaler ADC are affected by CVE-2023-4966?

CVE-2023-4966 presents critical security risk, a buffer overflow vulnerability rated CVSS 9.4.

Is CVE-2023-4966 being actively exploited?

Yes, CVE-2023-4966 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, confirming active in-the-wild exploitation. Immediate patching is required.

How to fix or mitigate CVE-2023-4966?

Within 24 hours: Identify all affected systems and apply vendor patches immediately. Monitor vendor channels for patch availability.

NetScaler ADC CVE-2023-4966

CRITICAL

Buffer Overflow (CWE-119)

2023-10-10 secure@citrix.com

9.4

CVSS 3.1

CVSS VectorNVD

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

Low

Lifecycle Timeline

Analysis Generated

Mar 26, 2026 - 11:19 vuln.today

Added to CISA KEV

Oct 24, 2025 - 13:42 cisa

CISA KEV

CVE Published

Oct 10, 2023 - 14:15 nvd

CRITICAL 9.4

DescriptionNVD

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.

AnalysisAI

Citrix NetScaler ADC and Gateway contain an information disclosure vulnerability known as 'CitrixBleed' that leaks sensitive session tokens from memory, enabling authenticated session hijacking at massive scale.

Technical ContextAI

The CWE-119 buffer over-read in NetScaler's HTTP/HTTPS handling leaks data from adjacent memory, including valid session cookies. An unauthenticated attacker can send crafted requests to extract session tokens from the appliance's memory, then replay these tokens to hijack active user sessions.

Affected ProductsAI

NetScaler ADC and Gateway configured as VPN, ICA Proxy, CVPN, RDP Proxy, or AAA virtual server

RemediationAI

Apply Citrix patches immediately. Terminate ALL active sessions after patching (session tokens already in attacker hands remain valid). Rotate all credentials. Monitor for unauthorized access using hijacked sessions.

CVE-2023-4966 vulnerability details – vuln.today

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