CVE-2004-1105 in Contivity VPN Client
Summary
by MITRE
Nortel Networks Contivity VPN Client displays a different error message depending on whether the username is valid or invalid, which could allow remote attackers to gain sensitive information.
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Analysis
by VulDB Data Team • 11/21/2024
The vulnerability identified as CVE-2004-1105 affects the Nortel Networks Contivity VPN Client implementation, representing a classic information disclosure flaw that exploits inconsistent error handling mechanisms. This vulnerability operates at the authentication layer of the VPN client software where the system provides different error responses based on the validity of user credentials. When an attacker attempts to authenticate with the VPN client, the system's response varies depending on whether the provided username exists in the system's user database, creating a predictable pattern that can be exploited for reconnaissance purposes. The flaw essentially creates a side-channel information leak that reveals whether a specific username is registered within the system, enabling attackers to perform user enumeration attacks against the VPN infrastructure.
This vulnerability directly maps to CWE-209, which describes "Information Exposure Through an Error Message" and falls under the broader category of information disclosure vulnerabilities. The technical implementation flaw stems from the client's failure to provide consistent error responses regardless of authentication outcome, violating fundamental security principles of uniform error handling. The system's behavior creates a deterministic pattern where valid usernames produce one type of error message while invalid usernames generate another, allowing attackers to distinguish between existing and non-existing user accounts through simple authentication attempts. This inconsistency in error messaging represents a significant weakness in the authentication protocol's design, as it provides attackers with actionable intelligence about the target system's user base without requiring any advanced exploitation techniques.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables attackers to conduct targeted credential brute force attacks with significantly reduced complexity. Once an attacker has enumerated valid usernames through this vulnerability, they can focus their efforts on cracking passwords for known accounts rather than attempting to guess user identities. The vulnerability affects the confidentiality aspect of the CIA triad by exposing user account information that should remain private, potentially enabling privilege escalation attacks or social engineering campaigns. In a corporate environment, this information disclosure could lead to targeted phishing attacks, account takeovers, or further reconnaissance activities that could compromise the entire network infrastructure.
Mitigation strategies for CVE-2004-1105 should focus on implementing consistent error handling across all authentication points within the VPN client software. Organizations should ensure that all authentication attempts, regardless of outcome, return identical error messages to prevent information leakage. This approach aligns with the principle of least information disclosure and follows security best practices outlined in various frameworks including the NIST Cybersecurity Framework and ISO 27001 standards. System administrators should also implement additional security controls such as account lockout mechanisms, rate limiting for authentication attempts, and monitoring for suspicious authentication patterns. The vulnerability demonstrates the importance of defensive programming practices and the need for thorough security testing of authentication mechanisms to prevent side-channel attacks that exploit implementation weaknesses rather than cryptographic flaws. Regular security assessments and penetration testing should include validation of error handling consistency across all network authentication systems to prevent similar vulnerabilities from being introduced in future implementations.