CVE-2026-20241 in Identity Services Engine
Summary
by MITRE • 11/04/2026
A vulnerability in the authorization mechanism of Cisco Identity Services Engine (ISE) and Cisco ISE Passive Identity Connector (ISE-PIC) could allow an unauthenticated, remote attacker to obtain an endpoint identity certificate.
This vulnerability is due to improper authorization checks. An attacker could exploit this vulnerability by sending a crafted request to an affected device. A successful exploit could allow the attacker to bypass authorization to obtain an endpoint certificate.
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Analysis
by VulDB Data Team • 11/04/2026
The Cisco Identity Services Engine and its Passive Identity Connector component serve as critical infrastructure for network access control, providing centralized authentication, authorization, and accounting services within enterprise environments. These systems are responsible for verifying the identity of devices attempting to connect to a network and enforcing security policies based on that identity. The vulnerability described herein resides in the core authorization mechanism of these platforms, specifically affecting how endpoint certificates are issued or accessed during the provisioning process. This flaw represents a significant deviation from expected secure coding practices regarding access control logic, allowing for unauthorized retrieval of sensitive cryptographic material that is intended to be restricted to authenticated and authorized administrative processes only.
The technical root cause of this vulnerability lies in improper authorization checks within the application layer handling certificate requests. When an endpoint seeks to join the network or update its credentials, it typically undergoes a rigorous authentication process involving EAP-TLS or similar protocols where certificates play a pivotal role. However, due to insufficient validation of the requester's permissions before processing specific API calls or internal service interactions related to certificate issuance, the system fails to enforce strict access controls. An unauthenticated, remote attacker can exploit this gap by sending crafted requests that mimic legitimate administrative operations but lack proper authentication tokens or session context. The server processes these requests as valid due to the missing verification step, thereby granting access to sensitive data structures containing endpoint identity certificates without requiring prior successful login or privilege escalation.
The operational impact of successfully exploiting this vulnerability is severe and multifaceted. By obtaining an endpoint identity certificate, an attacker gains a powerful tool for impersonation within the network infrastructure. These certificates are often used as primary credentials for device authentication; possessing one allows the attacker to bypass standard access control lists and gain unauthorized network access under the guise of a trusted entity. This can lead to lateral movement across segmented networks, interception of sensitive data transmitted by the compromised endpoint, or further exploitation of services that trust these identities. Furthermore, since ISE is often integrated with other security systems like SIEMs and firewalls, compromising its certificate authority functions could undermine the integrity of broader security monitoring and enforcement mechanisms, potentially leading to a complete compromise of network visibility and control.
From a classification perspective, this vulnerability aligns closely with CWE-284 Improper Access Control, as it involves failing to restrict access to resources based on user privileges or authentication status. It also relates to CWE-306 Missing Authentication for Critical Function, where the system performs sensitive operations without verifying the identity of the actor. In terms of attack vectors and tactics, this exploit maps to MITRE ATT&CK techniques such as T1552 Unsecured Credentials, specifically the retrieval of private keys or certificates from a local system, which can then be used for lateral movement via T1021 Remote Services if those credentials are leveraged against other systems. The ability to obtain these artifacts remotely without authentication places this vulnerability in the highest severity category regarding potential impact on confidentiality and integrity.
Mitigation strategies must focus immediately on patching the affected software versions provided by Cisco, as vendor-supplied updates typically address such logic flaws through code corrections that enforce proper session validation before processing certificate-related requests. In environments where immediate patching is not feasible due to operational constraints, network segmentation should be reviewed to ensure that ISE management interfaces are accessible only from trusted administrative subnets via firewalls or ACLs. Additionally, enabling strict logging and monitoring for anomalous patterns in authentication logs can help detect attempted exploitation activities. Organizations should also audit their certificate lifecycle management processes to minimize the value of any single compromised credential by implementing shorter validity periods and automated rotation policies where applicable, thereby reducing the window of opportunity for attackers leveraging stolen certificates.