CVE-2025-5777 in NetScaler ADC
Summary
by MITRE • 06/17/2025
Insufficient input validation leading to memory overread when the NetScaler is configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server
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Analysis
by VulDB Data Team • 10/31/2025
This vulnerability represents a critical memory safety issue within Citrix NetScaler appliances that can lead to information disclosure through improper input validation mechanisms. The flaw manifests when the appliance is configured as a Gateway serving various protocols including VPN virtual servers, ICA Proxy, CVPN, RDP Proxy, or AAA virtual servers. The insufficient input validation allows malicious actors to craft specially formatted requests that trigger memory overread conditions, potentially exposing sensitive data from the application's memory space.
The technical implementation of this vulnerability stems from inadequate bounds checking and input sanitization within the NetScaler's processing pipelines for gateway configurations. When legitimate requests pass through these vulnerable components, the system fails to properly validate the length and content of incoming data, allowing attackers to manipulate input parameters to cause the application to read beyond allocated memory boundaries. This overread behavior can potentially expose kernel memory contents, configuration data, session information, or other sensitive system artifacts that should remain protected from unauthorized access.
From an operational perspective, this vulnerability presents significant risk to organizations relying on NetScaler for secure access control and remote desktop services. Attackers could leverage this weakness to extract confidential information including authentication credentials, session tokens, system configurations, or other sensitive data that could be used for further exploitation or lateral movement within the network. The impact extends beyond simple information disclosure as the leaked memory contents might contain cryptographic keys, user credentials, or other critical system components that could compromise the entire security posture of the affected environment.
The vulnerability aligns with CWE-129, which addresses insufficient input validation, and maps to ATT&CK technique T1005 for data from local system. Organizations should prioritize immediate patching of affected NetScaler appliances to address this memory overread condition. Additional mitigations include implementing network segmentation, monitoring for suspicious traffic patterns, and deploying intrusion detection systems to detect potential exploitation attempts. Security teams should also conduct comprehensive vulnerability assessments to identify all NetScaler instances that may be configured as gateways and ensure proper input validation mechanisms are in place to prevent similar issues in other components of the system.