Is CVE-2023-4966 in the CISA KEV catalog?

Yes. CVE-2023-4966 is on the CISA Known Exploited Vulnerabilities list, added 2023-10-18, and has known ransomware campaign use.

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

CVE-2023-4966 has a CVSS v3 base score of 9.4 (CRITICAL).

What is the EPSS score for CVE-2023-4966?

CVE-2023-4966 has an EPSS score of 100.00% (100th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2023-4966?

Upgrade netscaler application delivery controller to 12.1-55.300 or later. Fixes are available for 2 affected products.

CVE & CISA-KEV Catalog

CVE-2023-4966

CRITICALCISA KEVEPSS 100th pctl

9.4

CVSS v3

NVD

Description

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.

CWE-119Buffer Overflow

How to fix

Remediation Available

netscaler application delivery controllerNVD

Affected:>= 12.1, < 12.1-55.300Fixed in:12.1-55.300CVE-2023-4966derived from NVD

Affected:>= 13.1, < 13.1-37.164Fixed in:13.1-37.164CVE-2023-4966derived from NVD

Affected:>= 14.1, < 14.1-8.50Fixed in:14.1-8.50CVE-2023-4966derived from NVD

netscaler gatewayNVD

Affected:>= 14.1, < 14.1-8.50Fixed in:14.1-8.50CVE-2023-4966derived from NVD

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityLow

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

Exploit Intelligence

100.00%probability of exploitation in 30 days

100thpercentile

Very high risk: more likely to be exploited than 100% of all known CVEs.

Known Exploited Vulnerability (CISA KEV)

Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow Vulnerability

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.

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.

Remediation due: 2023-11-08

Associated with ransomware campaigns

References

Vendor Advisory1

support.citrix.com

Third-Party Advisory1

packetstormsecurity.com

Government Resource1

cisa.gov

Related Vulnerabilities

Other CWE-119 (Buffer Overflow) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2017-11882	High	7.8	100%	KEV + Ransom	-
CVE-2020-0796	Critical	10.0	100%	KEV + Ransom	-
CVE-2008-4250	Critical	9.8	99%	KEV	-
CVE-2017-15944	Critical	9.8	98%	KEV	Fix
CVE-2015-0014	High	10.0	97%	-	-
CVE-2015-3105	High	10.0	96%	-	-

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-10-24.