CVE-2004-2621 in Contivity VPN Client
Summary
by MITRE
Nortel Contivity VPN Client 2.1.7, 3.00, 3.01, 4.91, and 5.01, when opening a VPN tunnel, does not check the gateway certificate until after a dialog box has been displayed to the user, which creates a race condition that allows remote attackers to perform a man-in-the-middle (MITM) attack.
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Analysis
by VulDB Data Team • 06/07/2017
The vulnerability identified as CVE-2004-2621 affects multiple versions of the Nortel Contivity VPN Client software, specifically versions 2.1.7, 3.00, 3.01, 4.91, and 5.01. This security flaw represents a critical design weakness in the client's certificate validation process that fundamentally undermines the integrity of VPN communications. The issue stems from a fundamental misalignment in the sequence of operations during the VPN tunnel establishment process, creating a window of opportunity for malicious actors to exploit the system.
The technical flaw manifests as a race condition within the certificate validation mechanism where the VPN client defers the verification of the gateway certificate until after the user interface has already displayed a dialog box. This temporal gap between certificate presentation and validation allows attackers to intercept and manipulate the communication channel before the client performs its security checks. The vulnerability specifically targets the client-side certificate validation process, which is designed to ensure that users are connecting to legitimate VPN gateways and not to malicious intermediaries. This flaw directly violates the principles of secure communication protocols where certificate validation should occur before any user interaction or data exchange begins.
The operational impact of this vulnerability is severe and far-reaching, as it enables remote attackers to execute successful man-in-the-middle attacks against unsuspecting users. Attackers can exploit this race condition to present fake certificates to users while the dialog box is displayed, making it appear as though they are connecting to a legitimate VPN gateway. This allows attackers to intercept, modify, or steal sensitive data transmitted through the VPN tunnel, including login credentials, personal information, and confidential business data. The vulnerability affects organizations that rely on Nortel Contivity VPN solutions for secure remote access, potentially compromising the confidentiality and integrity of their network communications. This issue particularly impacts enterprises with remote workers or distributed teams who depend on secure VPN connections for accessing corporate resources.
The vulnerability maps directly to CWE-310, which addresses cryptographic issues related to improper certificate validation timing and race conditions in security protocols. From an ATT&CK framework perspective, this vulnerability aligns with techniques such as T1573.002 (Encrypted Channel) and T1046 (Network Service Scanning) as attackers can establish malicious connections and maintain persistence. Organizations should implement immediate mitigations including updating to patched versions of the Nortel Contivity VPN Client, implementing additional authentication layers, and deploying network monitoring solutions to detect anomalous certificate behavior. The recommended approach includes configuring certificate pinning mechanisms, establishing network segmentation, and implementing comprehensive security awareness training for users to recognize potential man-in-the-middle attack indicators. Additionally, organizations should consider alternative VPN solutions that properly implement certificate validation before user interaction to prevent similar vulnerabilities from occurring in their network infrastructure.