CVE-2025-20337: Cisco ISE Critical RCE Vulnerability

Summary

CVE-2025-20337 is a critical remote code execution (RCE) vulnerability affecting Cisco Identity Services Engine (ISE) and Cisco ISE Passive Identity Connector (ISE-PIC). It allows unauthenticated, remote attackers to execute arbitrary commands as the root user with a specially crafted API request due to insufficient input validation in the API logic.

• CVSS Score: 10.0 (Critical)
• Affected Products: Cisco ISE 3.3 (pre-Patch 7), Cisco ISE 3.4 (pre-Patch 2), and corresponding ISE-PIC versions
• Attack Vector: Remote; no authentication required

23-07-2025 Update: As per latest Cisco Advisory – this vulnerability is exploited in the wild

Technical Details

Vulnerability Root Cause

• CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component (Command Injection).
• The vulnerable API does not properly validate user-supplied input, enabling attackers to inject malicious data that gets executed with root privileges on the underlying OS.

Exploitation Mechanics

• Access Required: None; the attacker does not need to authenticate.
• Exploit Step-by-Step:
  • The attacker crafts a malicious API request designed to exploit the input validation flaw.
  • The request is submitted to a vulnerable Cisco ISE or ISE-PIC API endpoint.
  • If unpatched, the device processes the request, executes the injected commands, and provides root-level access to the attacker.
• Impact: Full remote system takeover, including uploading and executing files, persistent installation of malware, full data access, and disabling of security controls.
• Exploitation Complexity: Low—no credentials, complex interaction, or social engineering required.

Note: Cisco and major security sources affirm that, as of the latest reporting, there is no evidence of public exploitation in the wild. However, the ease of exploitation and criticality demand immediate action.

Exploitation Prerequisites

• API management and administrative interfaces accessible from untrusted or public networks greatly increase the risk of exploitation.
• Devices running vulnerable versions (ISE 3.3 before Patch 7, ISE 3.4 before Patch 2) are at risk even if previously patched for other critical flaws such as CVE-2025-20281 or CVE-2025-20282.

Mitigation and Recommendations

• Upgrade immediately to:
  • Cisco ISE 3.4 Patch 2 or newer
  • Cisco ISE 3.3 Patch 7 with all recommended hotfixes
• No workarounds exist. Patching is the only solution.
• Restrict exposure: Limit API and admin interface access to trusted, internal networks; update firewall rules.
• Monitoring: Proactively audit logs for suspicious API or authentication activity.

Table: Affected Versions and Fixed Releases

Notes for Security Teams

• Detection: Unusual API activity and unauthorized root-level changes may indicate exploitation. No proof-of-concept exploits have appeared publicly, but rapid exploit development is highly likely.
• Devices remain vulnerable until upgraded; patching prior related vulnerabilities does not remediate CVE-2025-20337.

Discovery and Disclosure

• Discovered by Kentaro Kawane (GMO Cybersecurity) and reported through Trend Micro’s Zero Day Initiative.
• Publicly disclosed and coordinated with Cisco and major security outlets on July 17, 2025.

Immediate patching is mandatory for all affected Cisco ISE and ISE-PIC deployments to prevent complete system compromise.