CVE-2025-20337: Actionable Report for SOC Teams

Analysis

Amazon’s threat intel team identified an advanced threat actor leveraging two zero‑day vulnerabilities—CVE‑2025‑20337 in Cisco Identity Services Engine and CVE‑2025‑5777 in Citrix NetScaler ADC—to deploy a custom in‑memory Java web shell targeting Cisco ISE appliances.

Investigation

The activity was first flagged by Amazon’s MadPot honeypot network. Analysts observed exploit attempts against CVE‑2025‑5777 and CVE‑2025‑20337, followed by delivery of a custom back‑door named IdentityAuditAction. The web shell runs entirely in memory, uses Java reflection, registers a listener on the Tomcat server, and encrypts traffic with DES and a non‑standard Base64 encoding. Amazon attributes the campaign to a highly resourced actor with zero‑day capability and knowledge of enterprise Java and network‑edge appliances.

Mitigation

Apply the vendor‑released patches for CVE‑2025‑20337 (Cisco) and CVE‑2025‑5777 (Citrix) immediately. Restrict network access to management interfaces using firewalls, VLAN segmentation, and zero‑trust controls. Deploy host‑based intrusion detection to monitor unexpected Java processes, Tomcat modifications, and abnormal HTTP traffic. Enable multi‑factor authentication for administrative accounts and regularly audit privileged access.

Response

Patch vulnerable Cisco ISE and Citrix NetScaler devices, isolate compromised systems, and remove the custom web shell. Conduct forensic analysis of logs and memory dumps to identify indicators of compromise. Update detection rules in SIEM and IDS/IPS for the exploit payloads and web‑shell signatures. Notify relevant stakeholders and, if required, report the incident to appropriate authorities.

Payload Simulation

Simulation Execution
Prerequisite: The Telemetry & Baseline Pre‑flight Check must have passed.

• Attack Narrative & Commands:

  Initial Access: Attacker discovers an unauthenticated file‑upload endpoint on the Cisco ISE web interface.
•  
• Web Shell Deployment: Using curl, the attacker uploads webshell.jar disguised as iseComponent.jar. The JAR contains a malicious servlet that, when invoked, executes arbitrary Java code via reflection (java.lang.reflect.Method.invoke).
•  
• Obfuscation: The payload inside the servlet is DES‑encrypted and encoded with a custom Base64 variant to evade simple pattern matching.

   

• Execution Trigger: The attacker sends a forged HTTP request that causes the ISE process to launch the servlet, resulting in a command line similar to:

  java -cp /opt/cisco/ise/webapps/iseComponent.jar -Dpayload=DES:U2FsdGVkX1+... Base64:QmFzZTY0RW5jb2RlZURhdGE=Copy

• Logging: Cisco ISE logs an IdentityAuditAction event with the full command line, satisfying the detection rule conditions.

• Regression Test Script:

  #!/usr/bin/env bash
  set -euo pipefail
  
  # Variables
  ISE_HOST="https://ise.example.com"
  UPLOAD_ENDPOINT="${ISE_HOST}/admin/uploadComponent"
  SHELL_JAR="webshell.jar"
  MALICIOUS_PAYLOAD="U2FsdGVkX1+..."   # DES‑encrypted, custom Base64
  CUSTOM_B64="QmFzZTY0RW5jb2RlZURhdGE="