CVE-2018-0134 in Policy Suite
Summary
by MITRE
A vulnerability in the RADIUS authentication module of Cisco Policy Suite could allow an unauthenticated, remote attacker to determine whether a subscriber username is valid. The vulnerability occurs because the Cisco Policy Suite RADIUS server component returns different authentication failure messages based on the validity of usernames. An attacker could use these messages to determine whether a valid subscriber username has been identified. The attacker could use this information in subsequent attacks against the system. Cisco Bug IDs: CSCvg47830.
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Analysis
by VulDB Data Team • 02/02/2021
The vulnerability described in CVE-2018-0134 represents a significant information disclosure weakness within Cisco Policy Suite's RADIUS authentication framework. This flaw exists in the server component that handles authentication requests, creating a predictable pattern in error responses that can be exploited by malicious actors. The vulnerability specifically affects the RADIUS server implementation within Cisco Policy Suite, which is commonly deployed in service provider environments to manage subscriber access and authentication. The issue stems from the inconsistent error messaging behavior when processing authentication requests, where the system provides different responses depending on whether the username exists in the system. This type of vulnerability falls under the category of information leakage through error responses, which is classified as CWE-209 in the Common Weakness Enumeration catalog. The vulnerability is particularly concerning because it operates at the authentication layer, which is a critical security control point in network infrastructure.
The technical exploitation of this vulnerability relies on the attacker's ability to send authentication requests to the RADIUS server and analyze the subtle differences in error messages returned. When an attacker submits an authentication request with a non-existent username, the system generates one type of error response, whereas when a valid username but incorrect password is provided, the server returns a different error message. This differential response behavior creates a timing attack vector where an attacker can systematically test usernames and observe the server's response patterns to determine which usernames are valid within the system. The attacker does not require any authentication credentials to perform this reconnaissance, making the attack surface particularly broad. The vulnerability is classified under the ATT&CK technique T1110.001 for Brute Force/Password Guessing, as it provides information that significantly reduces the complexity of subsequent authentication attempts.
The operational impact of this vulnerability extends beyond simple username enumeration, as it creates a foundation for more sophisticated attacks against the affected system. Once an attacker has identified valid usernames, they can proceed with targeted password guessing, credential stuffing, or other attack vectors that would otherwise be significantly more difficult to execute. The vulnerability affects service providers who rely on Cisco Policy Suite for subscriber management, potentially compromising thousands of user accounts across the network. The impact is particularly severe in environments where the RADIUS server is used to authenticate users for network access, wireless services, or VPN connections, as the exposed usernames could provide access to critical network resources. The vulnerability demonstrates a fundamental flaw in the server's error handling mechanism, where security considerations were not properly integrated into the design of error responses.
Mitigation strategies for CVE-2018-0134 focus on standardizing error responses to prevent information leakage while maintaining system functionality. Organizations should implement consistent error messaging that does not differentiate between invalid usernames and invalid passwords, ensuring that all authentication failures return identical responses to prevent username enumeration. The recommended approach involves updating Cisco Policy Suite to versions that address the specific vulnerability identified in Cisco Bug ID CSCvg47830, which includes patches that normalize the authentication failure responses. Network administrators should also consider implementing additional security controls such as account lockout mechanisms, rate limiting for authentication attempts, and monitoring for unusual authentication patterns. The mitigation aligns with security best practices outlined in the NIST Cybersecurity Framework and ISO/IEC 27001 standards, which emphasize the importance of secure error handling and information protection. Additionally, implementing proper logging and monitoring can help detect exploitation attempts and provide early warning of potential attacks targeting this vulnerability.