CVE-2023-20194 in Identity Services Engine
Summary
by MITRE • 09/07/2023
A vulnerability in the ERS API of Cisco ISE could allow an authenticated, remote attacker to read arbitrary files on the underlying operating system of an affected device. To exploit this vulnerability, an attacker must have valid Administrator-level privileges on the affected device. This vulnerability is due to improper privilege management in the ERS API. An attacker could exploit this vulnerability by sending a crafted request to an affected device. A successful exploit could allow the attacker to elevate their privileges beyond the sphere of their intended access level, which would allow them to obtain sensitive information from the underlying operating system. Note: The ERS is not enabled by default. To verify the status of the ERS API in the Admin GUI, choose Administration > Settings > API Settings > API Service Settings.
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Analysis
by VulDB Data Team • 09/07/2023
This vulnerability resides within the External REST Services API of Cisco Identity Services Engine version 2.4 and later, representing a critical privilege escalation flaw that could enable authenticated attackers to access sensitive system resources. The vulnerability stems from inadequate input validation and privilege management within the API implementation, specifically affecting the authorization mechanisms that govern access to system files. The flaw allows an attacker with valid administrator credentials to manipulate API requests in ways that bypass normal access controls, creating a pathway for arbitrary file read operations on the underlying operating system.
The technical exploitation of CVE-2023-20194 requires an attacker to possess legitimate administrator-level privileges on the Cisco ISE device, which significantly reduces the attack surface but does not eliminate the risk entirely. The vulnerability manifests through improper handling of file path parameters in API requests, where the system fails to adequately sanitize user-supplied input before processing file system operations. This weakness falls under the CWE-22 category of Improper Limitation of a Pathname to a Restricted Directory, commonly known as Path Traversal, and represents a classic privilege escalation vector within web application security frameworks. The attack requires careful crafting of API requests that leverage the existing administrative access to manipulate the underlying file system operations.
The operational impact of this vulnerability extends beyond simple information disclosure, as successful exploitation could provide attackers with access to critical system files, configuration data, and potentially sensitive credentials stored within the operating system. This access could enable further compromise of the device through the extraction of encryption keys, system configuration files, or other sensitive artifacts that could be used for additional attacks. The vulnerability's severity is amplified by the fact that it operates within a privileged API interface that is designed for administrative functions, meaning that any successful exploitation would provide attackers with elevated access that could be leveraged for lateral movement within a network or for more sophisticated attacks. The ERS API's default disabled state provides some protection, but when enabled, it creates a significant security risk that requires immediate attention.
Mitigation strategies should focus on both immediate operational fixes and long-term architectural improvements to prevent similar privilege management failures. Organizations should first ensure that the ERS API is disabled when not actively required for administrative functions, as this provides the most effective immediate protection against exploitation. Cisco has released patches addressing this vulnerability that should be deployed immediately across all affected systems. Additionally, implementing network segmentation and access controls around ISE devices can limit the potential impact if the vulnerability is exploited. Security monitoring should include detection of unusual API request patterns and file access attempts that could indicate exploitation attempts. The ATT&CK framework categorizes this vulnerability under T1078 Valid Accounts and T1566 Phishing, as it requires legitimate administrative credentials for exploitation, and T1005 Data from Local System, as it allows access to sensitive local files. Regular security audits of API implementations and privilege management controls should be conducted to identify similar weaknesses in other systems and prevent future incidents.