CVE-2026-20235 in Identity Services Engine
Summary
by MITRE • 09/16/2026
A vulnerability in the API of Cisco Identity Services Engine (ISE) could allow an authenticated, remote attacker to view sensitive information on an affected device. To exploit this vulnerability, the attacker must have valid administrative credentials.
This vulnerability is due to insufficient validation of user-supplied parameters in API requests. An attacker could exploit this vulnerability by sending a crafted API request to an affected device. A successful exploit could allow the attacker to gain access to sensitive information, including hashed credentials that could be used in future attacks.
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Analysis
by VulDB Data Team • 09/16/2026
The Cisco Identity Services Engine (ISE) serves as a critical component in modern network security architectures, providing authentication, authorization, and accounting services for users and devices connecting to enterprise networks. Within this ecosystem, the ISE API acts as the primary interface for automation, integration with third-party systems, and administrative management of policy sets and user databases. The vulnerability identified herein resides within the input validation mechanisms governing these API endpoints. Specifically, the flaw stems from insufficient sanitization and type checking of parameters supplied by clients during API calls. While Cisco ISE is designed to enforce strict access controls requiring valid administrative credentials for most operations, this particular weakness allows an attacker who has already obtained such credentials to bypass internal logic checks that should restrict data exposure. This scenario highlights a common challenge in web application security where authentication serves as the first line of defense but fails to prevent logical flaws or improper object reference vulnerabilities once trust is established through valid session tokens or API keys.
From a technical perspective, this vulnerability classifies under CWE-209, which describes the generation of an error message that includes sensitive information, and potentially CWE-778, insufficient input validation leading to exposure of sensitive data. The core issue lies in how the application processes user-supplied parameters without adequately verifying their scope or intended output format. When a crafted API request is transmitted with specific malformed or unexpected parameter values, the backend processing logic fails to properly filter or restrict the response payload. Instead of returning an appropriate error code indicating invalid input, the system proceeds to process the request and returns detailed internal state information. This behavior effectively turns authenticated administrative access into a vector for data exfiltration, as the attacker can iteratively probe different endpoints and parameters to map out sensitive configuration details, network topology, or user database structures that were not intended for programmatic retrieval via those specific API methods.
The operational impact of this vulnerability is significant due to its reliance on authenticated access. Although an unauthenticated remote code execution would be more severe in terms of initial access requirements, the ability to extract hashed credentials from a system like ISE poses a substantial long-term risk. Hashed passwords stored within the Identity Services Engine are often used for local authentication or synchronization with external identity providers such as Active Directory or LDAP servers. If an attacker obtains these hashes, they can employ offline brute-force attacks using tools like John the Ripper or Hashcat to recover plaintext credentials. The compromise of administrative accounts further exacerbates this risk, allowing the attacker to modify security policies, disable logging mechanisms, or create backdoor access points within the network infrastructure. This aligns with ATT&CK technique T1078, Valid Accounts, as the exploitation depends entirely on the prior compromise of legitimate credentials, and T1530, Data from Cloud Storage Objects, if viewed through the lens of extracting data from managed services or internal repositories via API abuse.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. The primary defense is to apply the vendor-provided software patches that correct the input validation logic within the affected ISE versions. Organizations should prioritize updating their Identity Services Engine appliances as soon as these updates are available from Cisco Security Advisories. In addition to patching, network segmentation plays a crucial role in limiting exposure; API endpoints should be restricted to management VLANs or specific trusted IP ranges using firewall rules and access control lists (ACLs). Furthermore, implementing strict rate-limiting on API calls can help detect and mitigate automated probing attempts that characterize exploitation of this flaw. Security teams should also audit their administrative account usage, ensuring the principle of least privilege is enforced by removing unnecessary API permissions from standard administrator accounts where possible. Regular monitoring for anomalous API traffic patterns, such as unusual parameter values or high-frequency requests to sensitive endpoints, can provide early detection indicators before significant data exfiltration occurs.