Summary
CVE-2025-20337 is a critical Cisco ISE/ISE-PIC flaw letting unauthenticated attackers run code as root via crafted API requests. It affects versions 3.3.0 and 3.4.0; fixed in 3.3 Patch 7 and 3.4 Patch 2. Patch immediately, restrict API access, and monitor requests to prevent full system takeover.
Urgent Actions Required
- Update Cisco ISE/ISE-PIC to 3.3 Patch 7 or 3.4 Patch 2 immediately; earlier hot patches don’t fix the issue.
- Restrict API access with firewalls and network segmentation.
- Monitor for suspicious API requests.
- Enforce strong access controls and review Cisco ISE systems for signs of compromise.
Which Systems Are Vulnerable to CVE-2025-20337?
Technical Overview
- Vulnerability Type: Improper Input Handling in API leading to Remote Code Execution
- Affected Software/Versions:
- Cisco Identity Services Engine (ISE) 3.3.0 (including Patch 1–6)
- Cisco Identity Services Engine (ISE) 3.4.0 (including Patch 1)
- Cisco ISE Passive Identity Connector (ISE-PIC) for the above versions
- Attack Vector: Network
- CVSS Vector: CVSS:3.1
- Attack Vector: Network
- Attack Complexity: Low
- Privileges Required: None
- User Interaction: None
- Scope: Changed
- Confidentiality Impact: High
- Integrity Impact: High
- Availability Impact: High
- Patch Availability: Yes, available[1]
How Does the CVE-2025-20337 Exploit Work?
The attack typically follows these steps:
What Causes CVE-2025-20337?
Vulnerability Root Cause:
This flaw originates from poor API input validation in Cisco ISE and ISE-PIC. Malicious requests can bypass checks, letting attackers run code as root without authentication or user action, leading to full system compromise.
How Can You Mitigate CVE-2025-20337?
If immediate patching is delayed or not possible:
- Limit external access to Cisco ISE and ISE-PIC APIs.
- Allow API requests only from trusted sources using firewalls or proxies.
- Monitor logs for unusual API activity.
- Enforce strict access controls until patches are applied.
- Regularly review for signs of exploitation attempts targeting the API.
Which Assets and Systems Are at Risk?
Asset Types Affected:
- Cisco Identity Services Engine (ISE) 3.3.0 (and patches)
- Cisco Identity Services Engine (ISE) 3.4.0 (and patches)
- Cisco ISE Passive Identity Connector (ISE-PIC)
Business-Critical Systems at Risk:
- Network access control platforms using Cisco ISE
- Identity and policy enforcement systems integrated with ISE/ISE-PIC
- Environments relying on ISE for sensitive data and authentication handling
Exposure Level:
- Internet-facing Cisco ISE/ISE-PIC deployments accessible via APIs
- Internal deployments where API access is not properly restricted
Will Patching CVE-2025-20337 Cause Downtime?
Patch application impact: Applying the patch follows Cisco’s regular maintenance process. Expected downtime is minimal and limited to standard update/restart cycles.
How Can You Detect CVE-2025-20337 Exploitation?
Exploitation Signatures:
- Watch for crafted HTTP requests sent to Cisco ISE services.
- Requests may attempt to trigger code execution through malicious input in the API.
MITRE ATT&CK Mapping:
- T1190[5] – Exploit Public-Facing Application
Indicators of Compromise (IOCs/IOAs):
- Unexpected activity from Cisco ISE services after receiving external requests.
- Execution of unauthorized commands without proper authentication.
Behavioral Indicators:
- ISE processes behaving abnormally following crafted API requests.
- Signs of remote execution attempts without valid credentials.
Alerting Strategy:
- Priority: Critical
- Generate alerts for suspicious inbound API requests targeting ISE.
- Monitor for execution events initiated outside of normal admin activity.
Remediation & Response
Patch/Upgrade Instructions:
- Cisco has released software updates that address this vulnerability.
Fixed in:- Cisco ISE Release 3.3 Patch 7
- Cisco ISE Release 3.4 Patch 2
Where Can I Find More Information on CVE-2025-20337?
- ^Cisco Identity Services Engine Unauthenticated Remote Code Execution Vulnerabilities
- ^NVD – cve-2025-20337
- ^CVE-2025-20337 – Cisco Identity Services Engine Injection Vulnerability – [Actively Exploited]
- ^CVE-2025-20337 : Remote Code Execution Vulnerability in Cisco Identity Services Engine
- ^https://attack.mitre.org/techniques/T1190/
CVSS Breakdown Table
| Metric | Value | Description |
|---|---|---|
| Base Score | 10.0 | Highest severity rating assigned by Cisco |
| Attack Vector | Network | Exploitable remotely over HTTP/HTTPS |
| Attack Complexity | Low | Exploitation does not require special conditions |
| Privileges Required | None | No authentication is needed to exploit |
| User Interaction | None | Exploitation does not require user actions |
| Scope | Changed | Exploitation can affect resources beyond the vulnerable Cisco ISE component |
| Confidentiality Impact | High | Exploit allows exposure of sensitive information |
| Integrity Impact | High | Exploit may permit unauthorized modification of data |
| Availability Impact | High | Successful attack can disrupt service availability |
