CVE-2017-6747 in Identity Services Engine
Summary
by MITRE
A vulnerability in the authentication module of Cisco Identity Services Engine (ISE) could allow an unauthenticated, remote attacker to bypass local authentication. The vulnerability is due to improper handling of authentication requests and policy assignment for externally authenticated users. An attacker could exploit this vulnerability by authenticating with a valid external user account that matches an internal username and incorrectly receiving the authorization policy of the internal account. An exploit could allow the attacker to have Super Admin privileges for the ISE Admin portal. This vulnerability does not affect endpoints authenticating to the ISE. The vulnerability affects Cisco ISE, Cisco ISE Express, and Cisco ISE Virtual Appliance running Release 1.3, 1.4, 2.0.0, 2.0.1, or 2.1.0. Release 2.2.x is not affected. Cisco Bug IDs: CSCvb10995.
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Analysis
by VulDB Data Team • 01/07/2021
The vulnerability identified as CVE-2017-6747 resides within the authentication module of Cisco Identity Services Engine (ISE) platforms, representing a critical flaw in access control mechanisms that could permit unauthorized administrative access to network infrastructure. This vulnerability specifically targets the improper handling of authentication requests and policy assignment processes for externally authenticated users, creating a pathway for malicious actors to exploit the system's trust model. The flaw manifests when an attacker authenticates using a valid external user account that coincidentally matches an internal username, allowing the system to incorrectly assign the authorization policy of the internal account to the external user. This misconfiguration creates a privilege escalation scenario where an unauthenticated remote attacker can effectively assume Super Admin privileges within the ISE Admin portal, bypassing local authentication mechanisms entirely. The vulnerability affects multiple versions of Cisco ISE including releases 1.3, 1.4, 2.0.0, 2.0.1, and 2.1.0, while versions 2.2.x remain unaffected, indicating that Cisco addressed this issue in subsequent releases through code modifications and policy enforcement improvements.
The technical exploitation of this vulnerability stems from a fundamental flaw in the authentication module's user identification and policy assignment logic, which fails to properly distinguish between internal and external user accounts despite sharing identical usernames. This misclassification occurs during the authentication process where the system incorrectly maps external authentication requests to internal user policies, effectively allowing external users to inherit the privileges and access rights of internal administrative accounts. The vulnerability demonstrates characteristics consistent with CWE-287 Improper Authentication, where insufficient validation of authentication requests leads to unauthorized access to protected resources. From an operational perspective, this flaw represents a significant risk to network security infrastructure, as it allows attackers to gain complete administrative control over the ISE platform without requiring valid credentials for the administrative interface. The impact extends beyond simple privilege escalation, as the attacker can manipulate network access policies, modify user accounts, and potentially gain visibility into sensitive network operations through the ISE Admin portal.
The operational implications of this vulnerability are severe given that it affects the core authentication and authorization functions of Cisco ISE, which serves as a critical component in network access control and identity management. Attackers exploiting this vulnerability could leverage the Super Admin privileges to modify access control policies, create new administrative accounts, or disable security controls within the ISE environment. This compromise directly violates the principle of least privilege and could lead to widespread network infiltration, as the ISE platform typically controls access to critical network resources and endpoints. The vulnerability's remote exploitability means that attackers need not have physical access to the network infrastructure, making it particularly dangerous in environments where network security is paramount. According to ATT&CK framework mappings, this vulnerability aligns with T1078 Valid Accounts and T1484 Defense Evasion techniques, as it exploits legitimate authentication mechanisms to maintain persistent access and evade detection while establishing administrative control over network access policies.
Organizations affected by this vulnerability should immediately implement mitigations including applying the relevant Cisco security patches and updates, particularly for versions 1.3 through 2.1.0 where the flaw exists. Network segmentation and monitoring of authentication events should be enhanced to detect unusual policy assignment patterns that may indicate exploitation attempts. The implementation of additional authentication controls such as multi-factor authentication for administrative access can provide defense-in-depth against similar vulnerabilities. Cisco has addressed this issue in release 2.2.x, making it imperative for organizations to upgrade their ISE platforms to these unaffected versions. Security teams should also conduct thorough audits of user account mappings and policy assignments to ensure that external and internal accounts do not share identical usernames that could trigger this vulnerability. The vulnerability serves as a reminder of the critical importance of proper authentication module design and the potential for seemingly minor implementation flaws to create significant security risks in network infrastructure platforms.