CVE-2023-4966

Citrix NetScaler ADC and NetScaler Gateway: Buffer Overflow

As of , CVE-2023-4966 in Citrix NetScaler ADC and NetScaler Gateway is on CISA's list of exploited vulnerabilities: CISA listed it on . Our patch-first group: Patch this week.

Exploited
Yes: CISA listed it on 18 October 2023
US federal deadline
8 November 202321 days after CISA listed it. US federal civilian agencies must fix it by then.
Used in ransomware campaigns
Known
EPSS score
0.99Higher than 99% of the CVEs EPSS scores. EPSS estimates the chance of exploitation activity in the next 30 days.
EPSS when listed
0.00 on 18 October 2023EPSS on the day CISA listed it.
Public exploit
1 Metasploit module
Fix
Vendor advice: www.netscaler.comLinks below, from CISA's entry.

What CISA says 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.

CISA's required action

What the flaw is

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.

CISA's 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.

The CVE record's description, from Citrix

CVE published
10 October 2023
Assigned by
Citrix
CVSS
9.4 Critical (CVSS 3.1, from the CNA)
CWE-119
Improper Restriction of Operations within the Bounds of a Memory Buffer
CISA SSVC, exploitation
active
CISA SSVC, automatable
yes
CISA SSVC, technical impact
total

Timeline

  1. The CVE record was published.
  2. CISA added it to its list of exploited vulnerabilities.
  3. The US federal deadline to fix it.

Public exploits

Facts from Metasploit's module list and Exploit-DB's index; we never copy exploit code.

  • Metasploit: Citrix ADC (NetScaler) Bleed Scannerauxiliary module, rank normal

NetScaler ADC and NetScaler Gateway: other exploited entries

VulnerabilityProductOur groupListedDeadlineEPSS
CVE-2023-3519Code InjectionCitrix NetScaler ADC and NetScaler GatewayPatch this weekRansomware use; Metasploit module; EPSS 0.990.99
CVE-2023-6549Buffer OverflowCitrix NetScaler ADC and NetScaler GatewayPatch this weekEPSS 0.580.58
CVE-2023-6548Code InjectionCitrix NetScaler ADC and NetScaler GatewayPatch soon0.03
CVE-2026-8452Improper Restriction of Operations within the Bounds of a Memory BufferCitrix NetScaler ADC and NetScaler GatewayPatch soon0.01

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