CVE-2026-20176: Cisco ISE Remote Code Execution Vulnerability

CVE-2026-20176 Overview

CVE-2026-20176 is a command injection vulnerability in Cisco Identity Services Engine (ISE) that allows an authenticated, remote attacker to execute arbitrary commands on the underlying operating system. Exploitation requires valid high-privileged administrative credentials. An attacker sends a crafted HTTP request to the affected device to trigger the flaw. Successful exploitation grants system-level access and enables privilege escalation to root. In single-node deployments, exploitation can render the ISE node unavailable, producing a denial-of-service condition where unauthenticated endpoints cannot access the network until the node is restored. The weakness is tracked under [CWE-77] (Improper Neutralization of Special Elements used in a Command).

Critical Impact
Authenticated attackers can obtain root-level access on Cisco ISE and disrupt network authentication services in single-node deployments.

Affected Products

Cisco Identity Services Engine (ISE)
Cisco ISE management web interface
Cisco ISE single-node deployments (DoS impact)

Discovery Timeline

2026-09-16 - CVE-2026-20176 published to NVD
2026-09-17 - Last updated in NVD database

Technical Details for CVE-2026-20176

Vulnerability Analysis

CVE-2026-20176 is a command injection flaw in the Cisco ISE management interface. The vulnerable code path processes HTTP request parameters without sufficient neutralization of shell metacharacters before passing them to an operating system command. An authenticated administrator can inject commands that the ISE application executes with elevated privileges on the host. From that initial code execution, the attacker can escalate to root on the underlying operating system.

In single-node ISE deployments, the same code path can be abused to crash or hang the ISE services, producing a denial-of-service condition. During that outage, endpoints that have not already authenticated cannot reach the network until the node is restored, disrupting RADIUS, TACACS+, and posture services that depend on ISE.

Root Cause

The root cause is insufficient validation of user-supplied input passed from an HTTP request into a system command invocation. Because input is not properly sanitized or parameterized, attacker-controlled data is interpreted as part of the command line rather than as opaque data.

Attack Vector

The attack vector is network-based against the ISE administrative interface. The attacker must first authenticate with valid high-privileged administrative credentials, then submit a crafted HTTP request containing injected command syntax. No user interaction is required. Because the impact scope changes and reaches the host operating system, the vulnerability affects confidentiality, integrity, and availability of the ISE node.

No public proof-of-concept code is available for this vulnerability. Refer to the Cisco Security Advisory for authoritative technical details.

Detection Methods for CVE-2026-20176

Indicators of Compromise

Unexpected HTTP requests to ISE administrative endpoints containing shell metacharacters such as ;, |, backticks, or $(...) in parameter values.
New or unexpected processes spawned by the ISE application user, or child processes of the web tier invoking /bin/sh, bash, curl, or wget.
Privilege escalation events resulting in root shells originating from the ISE web service.
ISE service crashes, restarts, or unavailability in single-node deployments correlated with administrative HTTP activity.

Detection Strategies

Inspect ISE application and web access logs for administrative HTTP requests containing command injection patterns.
Correlate authenticated admin sessions with subsequent OS-level command execution or new outbound connections from the ISE host.
Baseline the set of processes normally spawned by ISE services and alert on deviations.

Monitoring Recommendations

Forward ISE syslog, admin audit logs, and host telemetry to a centralized SIEM for correlation.
Alert on administrative logins from unusual source IPs or outside change windows.
Monitor for RADIUS/TACACS+ service degradation that could indicate exploitation of the DoS impact in single-node deployments.

How to Mitigate CVE-2026-20176

Immediate Actions Required

Review the Cisco Security Advisory and identify all ISE nodes in scope.
Apply the fixed ISE software release published by Cisco as soon as it is available in your environment.
Rotate ISE administrative credentials and audit all high-privileged admin accounts for legitimacy.
Restrict network access to the ISE administrative interface to a dedicated management network and trusted admin workstations.

Patch Information

Cisco has published guidance and fixed software information in the Cisco Security Advisory cisco-sa-ise-rce-se7bYU57. Consult the advisory for the specific fixed releases applicable to your ISE deployment and upgrade path.

Workarounds

Enforce strict role separation and limit the number of accounts with high-privileged administrative roles in ISE.
Require multi-factor authentication for all ISE administrator accounts to raise the bar for credential-based access.
Place ISE administrative interfaces behind access control lists that permit only known management hosts.
Deploy ISE in a distributed, redundant topology where feasible to reduce the impact of a single node becoming unavailable.

bash

# Configuration example: restrict ISE admin access to a management subnet
# Applied on an upstream firewall or ACL device
access-list ISE_ADMIN permit tcp 10.10.0.0 0.0.0.255 host <ISE_ADMIN_IP> eq 443
access-list ISE_ADMIN deny   tcp any host <ISE_ADMIN_IP> eq 443
access-list ISE_ADMIN permit ip any any