CVE-2026-20306 in Identity Services Engine Software
Summary
by MITRE • 09/16/2026
A vulnerability in the REST API of Cisco ISE and ISE-PIC could allow an authenticated, remote attacker to perform command injection attacks on the underlying operating system and elevate privileges to root. To exploit this vulnerability, the attacker must have valid administrative credentials.
This vulnerability is due to improper validation of user-supplied input. An attacker could exploit this vulnerability by sending crafted commands to the web-based management interface of an affected device. A successful exploit could allow the attacker to execute arbitrary code on the device and elevate privileges to root. In single-node deployments, successful exploitation of this vulnerability could cause the affected ISE node to become unavailable, resulting in a DoS condition. In that condition, endpoints that have not already authenticated would be unable to access the network until the node is restored.
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Analysis
by VulDB Data Team • 09/16/2026
The identified security flaw resides within the REST API implementation of Cisco Identity Services Engine and its associated Policy Information Center component, presenting a critical risk for organizations relying on these systems for network access control and policy enforcement. This vulnerability allows an authenticated remote attacker to execute arbitrary commands on the underlying operating system with root-level privileges. The core technical deficiency is rooted in improper validation of user-supplied input within the web-based management interface that exposes the REST API endpoints. When a request containing maliciously crafted command strings reaches the application layer, the software fails to adequately sanitize or escape special characters and shell metacharacters before passing them to system-level execution functions. This lack of rigorous input filtering creates a classic Command Injection vector, enabling an attacker to bypass intended application logic and inject operating system commands that are executed with the privileges of the service account running the ISE process.
From a threat modeling perspective, this vulnerability aligns closely with Common Weakness Enumeration CWE-78, which describes Improper Neutralization of Special Elements used in an OS Command, often referred to as OS Command Injection. The attack vector is classified under MITRE ATT&CK technique T1059, specifically command and scripting interpretation, allowing adversaries to leverage the compromised application interface for direct system interaction. Because exploitation requires valid administrative credentials, this flaw represents a significant insider threat or post-exploitation escalation path rather than an unauthenticated remote code execution vulnerability. However, once an attacker obtains these credentials through phishing, credential stuffing, or other means, they can immediately pivot from user-level access to full root control over the host operating system. This privilege escalation effectively compromises the integrity of the entire Identity Services Engine node, as root access permits modification of security configurations, extraction of sensitive data such as authentication secrets and certificates, and installation of persistent backdoors that are difficult to detect using standard monitoring tools.
The operational impact of this vulnerability extends beyond mere unauthorized command execution, particularly in single-node deployments where high availability is not guaranteed by a clustered architecture. In such environments, successful exploitation can lead to service instability or complete unavailability of the ISE node due to resource exhaustion, process crashes, or deliberate disruption caused by malicious commands. This denial-of-service condition has severe downstream effects on network security operations. Endpoints that have not yet completed authentication processes will be unable to obtain network access credentials from the compromised Identity Services Engine. Consequently, legitimate users may experience sudden loss of connectivity, and critical business applications relying on continuous identity verification could fail. The restoration of service requires manual intervention or system recovery procedures, during which the organization operates with reduced visibility into endpoint compliance and potential exposure to unauthorized devices attempting to connect without proper authentication checks.
Mitigation strategies must prioritize immediate patching if a vendor-supplied fix is available, as this addresses the root cause by implementing stricter input validation and output encoding within the REST API handlers. In cases where patching is not immediately feasible, network segmentation should be enforced to restrict access to the ISE management interfaces exclusively from trusted administrative subnets using firewalls or virtual LANs. Additionally, enforcing multi-factor authentication for all administrative accounts significantly raises the barrier for attackers seeking to obtain the valid credentials required to exploit this flaw. Security teams should also implement robust logging and monitoring solutions that detect anomalous API usage patterns, such as unusual command structures in REST requests or unexpected spikes in system-level process executions originating from ISE services. Regular audits of administrative access logs can help identify potential compromise attempts before they result in full root escalation, ensuring the integrity of the network identity infrastructure remains intact against this specific attack vector.