In recent disclosures, Cisco and Citrix have released urgent security updates for two sets of critical vulnerabilities affecting their NetScaler (formerly Citrix ADC) and Identity Services Engine (ISE) platforms. These vulnerabilities pose a serious risk to enterprises, allowing unauthenticated attackers to execute arbitrary code, steal session tokens, and bypass authentication protections. Organizations using these technologies should take immediate action to patch affected systems and review their security posture.
CitrixBleed 2: NetScaler Gateway Vulnerabilities Actively Exploited
Citrix has addressed multiple severe vulnerabilities in NetScaler ADC and NetScaler Gateway, some of which have already been exploited in the wild. Chief among them is CVE-2025-5777, dubbed CitrixBleed 2, a memory read flaw that can expose session tokens, credentials, and sensitive data from memory. A second vulnerability, CVE-2025-6543, involves a memory overflow condition leading to denial of service or potential code execution. Both flaws affect devices configured as a Gateway or AAA virtual server.
Security researchers warn that compromised appliances may remain backdoored even after patching, particularly if active sessions were not terminated. This attack vector closely mirrors the original CitrixBleed vulnerability from 2023, which was linked to nation-state espionage and ransomware campaigns.
To address these risks:
- Patch immediately to the latest supported versions: 14.1-47.46 or later for NetScaler ADC and Gateway
- Terminate all active ICA and PCoIP sessions post-patch using administrative commands
- Decommission end-of-life versions, such as NetScaler ADC/Gateway 12.1 and 13.0
Organizations should assess their exposure through regular penetration testing to identify attack paths that could lead to session hijacking or code execution. In addition, vulnerability management can help detect and prioritize unpatched NetScaler systems across the enterprise. For ongoing monitoring of suspicious behavior, managed SIEM enables early detection of anomalous session activity and reconnaissance attempts associated with exploitation.
Cisco ISE and ISE-PIC: Unauthenticated Remote Code Execution
On the access control front, Cisco has disclosed two maximum-severity (CVSS 10.0) vulnerabilities affecting its Identity Services Engine (ISE) and ISE Passive Identity Connector (ISE-PIC). The flaws, CVE-2025-20281 and CVE-2025-20282, allow unauthenticated attackers to gain root-level access through specially crafted API requests or malicious file uploads.
- CVE-2025-20281 impacts ISE/ISE-PIC versions 3.3 and 3.4. It results from insufficient input validation, enabling remote code execution as root.
- CVE-2025-20282 affects only version 3.4 and allows arbitrary files to be placed in privileged directories, leading to full system compromise.
These vulnerabilities require no user interaction and affect systems even when default configurations are used. Given ISE’s critical role in network access control and identity enforcement, successful exploitation can provide attackers with the keys to the network.
Cisco has not observed exploitation in the wild, but due to the ease of exploitation, security teams should treat this as a top priority:
- Upgrade to ISE 3.3 Patch 6 or 3.4 Patch 2 immediately
- Review ISE logs for suspicious file operations or unauthenticated API requests. After reviewing, terminate using:
- kill icaconnection -all
- kill pcoipconnection -all
- Audit administrative interfaces for unexpected access patterns
To defend against such flaws, nGuard recommends conducting a device configuration audit to identify weak access controls and exposed management interfaces. For organizations concerned about advanced persistent threats leveraging these flaws, penetration testing can simulate real-world attacks on NAC infrastructure to reveal exploitation paths. Ongoing vulnerability management will ensure prompt identification of future Cisco advisories, while managed SIEM provides 24/7 monitoring for API abuse and unauthorized access attempts.
Take Action Now
Whether your organization relies on NetScaler for remote access or Cisco ISE for identity enforcement, these vulnerabilities represent a significant threat. Applying the latest patches is only the first step. nGuard’s suite of services is designed to help organizations validate remediation, uncover hidden risks, and monitor for signs of exploitation.
Reach out to nGuard today to ensure your environment is secure against these evolving threats.