CVE-2023-4966 Citrix NetScaler ADC and NetScaler Gateway: memory-safety flaw
In plain words: The program mishandles the memory it uses to keep track of data. A specially made input can scramble that memory. Usually lets an attacker crash the program or run their own code with its permissions.
Confirmed exploited by CISA on · US federal patch deadline Nov 8, 2023
What to do
- Install Citrix's security update for NetScaler ADC and NetScaler Gateway. If no update exists, follow the vendor's workaround or stop using the product until one ships.
- Patch edge devices first — attackers often start scanning for them within hours of a fix.
- Never expose the device's admin page to the internet.
- After patching a device that was exposed, follow the vendor's compromise checks, end active sessions and change passwords.
Who is affected
Work IT. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.
What's at risk: They face the internet and guard the whole network, so a flaw here can hand attackers a way in — and these devices usually run no antivirus, so break-ins go unnoticed.
The details
- Official name
- Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow Vulnerability
- Product
- Citrix NetScaler ADC and NetScaler Gateway
- CISA description
- 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.
- Type of flaw
- Memory-safety flaw (CWE-119)
- Confirmed exploited
- Oct 18, 2023 — known to be used in ransomware attacks
- US federal patch deadline
- Nov 8, 2023
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Answering about CVE-2023-4966 ·
Questions about CVE-2023-4966
Is CVE-2023-4966 being exploited?
Yes. CISA added CVE-2023-4966 to its Known Exploited Vulnerabilities catalog on Oct 18, 2023, which means there is reliable evidence of real-world attacks, including by ransomware groups.
How do I fix CVE-2023-4966?
Install Citrix's security update for NetScaler ADC and NetScaler Gateway. If no update exists, follow the vendor's workaround or stop using the product until one ships. Patch edge devices first — attackers often start scanning for them within hours of a fix.
Am I affected by CVE-2023-4966?
Only if you use Citrix NetScaler ADC and NetScaler Gateway. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.