CVE-2025-6543 Citrix NetScaler ADC and 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 Jul 21, 2025
What to do
- Install Citrix's security update for NetScaler ADC and 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 Gateway Buffer Overflow Vulnerability
- Product
- Citrix NetScaler ADC and Gateway
- CISA description
- Citrix NetScaler ADC and Gateway contain a buffer overflow vulnerability leading to unintended control flow and Denial of Service. NetScaler must be configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server.
- Type of flaw
- Memory-safety flaw (CWE-119)
- Confirmed exploited
- Jun 30, 2025
- US federal patch deadline
- Jul 21, 2025
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Answering about CVE-2025-6543 ·
Questions about CVE-2025-6543
Is CVE-2025-6543 being exploited?
Yes. CISA added CVE-2025-6543 to its Known Exploited Vulnerabilities catalog on Jun 30, 2025, which means there is reliable evidence of real-world attacks.
How do I fix CVE-2025-6543?
Install Citrix's security update for NetScaler ADC and 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-2025-6543?
Only if you use Citrix NetScaler ADC and Gateway. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.