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How CVE-2025-6543 Works
CVE-2025-6543 is a critical memory overflow vulnerability in NetScaler ADC and NetScaler Gateway when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server. The flaw occurs due to improper boundary checks in memory handling, allowing an attacker to trigger a buffer overflow via specially crafted network packets. This overflow corrupts memory structures, leading to unintended control flow manipulation, potential remote code execution (RCE), or Denial of Service (DoS) by crashing the service. The attack exploits the VPN/AAA virtual server components, requiring no user interaction (UI:N) and leverages network access (AV:N) with high attack complexity (AC:H).
DailyCVE Form
Platform: NetScaler ADC/Gateway
Version: 13.1, 14.1
Vulnerability: Memory overflow
Severity: Critical
Date: 06/25/2025
Prediction: Patch by 08/15/2025
What Undercode Say
Analytics:
nmap -p 443 --script citrix-cve-2025-6543 <target> curl -X POST -d "malformed_packet" https://<target>/vpn/index.html
How Exploit:
- Crafted HTTP/HTTPS packets overflow memory buffers.
- Exploits VPN/AAA virtual server handlers.
- Bypasses ASLR via controlled memory corruption.
Protection from this CVE:
- Apply Citrix security updates immediately.
- Disable unused Gateway services.
- Enforce strict network ACLs.
Impact:
- Remote code execution.
- Service disruption (DoS).
- Unauthorized access escalation.
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
