EUVD-2025-19085CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
6Description
Memory overflow vulnerability leading to unintended control flow and Denial of Service in NetScaler ADC and NetScaler Gateway when configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server
Analysis
Citrix NetScaler ADC and Gateway contain a memory overflow vulnerability (CVE-2025-6543, CVSS 9.8) leading to unintended control flow and denial of service when configured as VPN or AAA virtual server. KEV-listed with public PoC, this vulnerability paired with CVE-2025-5777 (memory overread) indicates a systemic weakness in NetScaler's VPN request processing that enables both data theft and remote code execution.
Technical Context
Unlike the companion CVE-2025-5777 (memory overread for data theft), this vulnerability causes a memory overflow that corrupts control flow data. This can cause immediate denial of service (crashing the NetScaler) or, with careful exploitation, redirect execution to attacker-controlled code. The VPN/AAA functionality is the attack surface — the same components affected by the overread vulnerability, suggesting a shared root cause in request parsing.
Affected Products
['Citrix NetScaler ADC (when configured as Gateway VPN, ICA Proxy, CVPN, RDP Proxy)', 'Citrix NetScaler Gateway (when configured as Gateway or AAA virtual server)']
Remediation
Apply Citrix security update for both CVE-2025-6543 and CVE-2025-5777. Prioritize if VPN/AAA is internet-facing. Consider taking VPN offline if patching is delayed. After patching: invalidate sessions, rotate TLS keys.
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External POC / Exploit Code
Leaving vuln.today