CVE-2026-20147: Cisco ISE Remote Code Execution Vulnerability

Note

TL;DR: Cisco ISE and ISE-PIC are vulnerable to a critical command injection flaw (CVE-2026-20147, CVSS 9.9). An authenticated, remote administrator can execute arbitrary commands on the OS, leading to root privilege escalation. Immediate patching to the latest available release is mandatory.

Executive Summary

Cisco Identity Services Engine (ISE) and ISE-PIC possess a critical command injection vulnerability. This flaw allows an authenticated administrator to execute arbitrary commands on the underlying host operating system. The vulnerability originates from insufficient input validation in HTTP requests, which are processed by the device. If exploited, an attacker gains user-level access, followed by potential escalation to root, impacting the device’s availability and network security.

Technical Analysis

The vulnerability, tracked as CVE-2026-20147, is a command injection flaw categorized as CWE-77.

The injection point is situated in the handling of HTTP requests within the Cisco ISE management interface. Because the system fails to adequately sanitize user-supplied input, malicious payloads can be injected to escape the intended execution context and run OS-level commands.

While exploitation requires valid administrative credentials, the impact is severe due to the critical role of ISE within network access control.

Exploitation Flow

An attacker with administrative access submits a specially crafted HTTP request to the target Cisco ISE device. The application, failing to validate the request parameters, executes the embedded commands.

1. Authentication: Attacker authenticates as an administrator.
2. Crafted Request: Attacker sends an HTTP request containing malicious input.
3. Execution: The ISE system processes the input and executes commands on the underlying OS.
4. Escalation: The attacker escalates from the initial context to root privileges.

Forensic Investigation

Identify attempts to exploit this vulnerability by analyzing administrative access logs for unusual request patterns.

Traffic Analysis

Inspect management traffic (HTTPS) for unusual parameters or command injection syntax.

OS Logs

Monitor system logs for unexpected process execution originating from the web management service.

Detection

Detection relies on analyzing administrative traffic and system logs.

1. Audit Logs: Identify administrative accounts accessing the management interface from unusual source IPs.
2. Traffic Inspection: Use TLS offloading to inspect administrative HTTPS traffic for suspicious input patterns.
3. SIEM Monitoring: Correlate administrative logins with subsequent unusual process activity.

Mitigation

Cisco has released patches for the affected versions. There are no workarounds for this vulnerability.

• Cisco ISE 3.1: Upgrade to 3.1 Patch 11
• Cisco ISE 3.2: Upgrade to 3.2 Patch 10
• Cisco ISE 3.3: Upgrade to 3.3 Patch 11
• Cisco ISE 3.4: Upgrade to 3.4 Patch 6
• Cisco ISE 3.5: Upgrade to 3.5 Patch 3

Sources

• Cisco Security Advisory
• NVD Detail