CVE-2017-17543 in FortiClient
Summary
by MITRE
Users' VPN authentication credentials are unsafely encrypted in Fortinet FortiClient for Windows 5.6.0 and below versions, FortiClient for Mac OSX 5.6.0 and below versions and FortiClient SSLVPN Client for Linux 4.4.2335 and below versions, due to the use of a static encryption key and weak encryption algorithms.
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Analysis
by VulDB Data Team • 01/31/2020
This vulnerability resides in the Fortinet FortiClient VPN client software across multiple operating systems including Windows, macOS, and Linux platforms. The security flaw stems from the implementation of weak cryptographic practices where the software employs static encryption keys combined with inadequate encryption algorithms to protect user authentication credentials. This represents a fundamental failure in cryptographic implementation that directly compromises the confidentiality of sensitive authentication data. The vulnerability affects versions prior to 5.6.1 for Windows and macOS, and 4.4.2336 for Linux, indicating a widespread issue across the affected product lines.
The technical implementation of this vulnerability demonstrates a clear violation of established cryptographic best practices and security standards. The use of static encryption keys means that the same cryptographic material is reused across multiple encryption operations, making the system susceptible to cryptanalysis and pattern recognition attacks. This approach fundamentally undermines the security model of encryption, as static keys provide attackers with a fixed target for decryption attempts. The weak encryption algorithms employed further compound the issue by providing insufficient computational complexity to resist modern cryptographic attacks. This flaw aligns with common weakness patterns identified in the CWE database under categories related to cryptographic implementation errors and weak encryption algorithms.
The operational impact of this vulnerability is severe and multifaceted for organizations relying on FortiClient VPN solutions. Attackers who successfully exploit this weakness can extract stored VPN credentials without requiring additional authentication factors, potentially gaining unauthorized access to corporate networks and sensitive systems. The vulnerability creates a persistent threat vector where stolen credentials can be used for lateral movement, privilege escalation, and data exfiltration activities. This risk is particularly elevated in environments where users maintain access to critical infrastructure or sensitive data repositories, as compromised credentials can provide attackers with direct pathways to these resources. The impact extends beyond individual user accounts to potentially compromise entire network perimeters and organizational security postures.
Organizations should immediately implement mitigation strategies including upgrading to patched versions of FortiClient software that address the cryptographic weaknesses in encryption key management and algorithm selection. The recommended remediation involves comprehensive deployment of FortiClient versions 5.6.1 or later for Windows and macOS, and 4.4.2336 or later for Linux platforms. Security administrators should also consider implementing additional authentication mechanisms such as multi-factor authentication to reduce the impact of credential compromise. Network monitoring should be enhanced to detect unusual authentication patterns that might indicate credential theft or unauthorized access attempts. This vulnerability demonstrates the critical importance of proper cryptographic implementation and the potential consequences of failing to maintain up-to-date security practices. The issue also highlights the need for organizations to maintain comprehensive inventory management of all VPN client software versions and ensure timely patch deployment across all endpoints. Organizations should conduct thorough risk assessments to identify systems that may be vulnerable and implement appropriate access controls to limit potential damage from credential compromise.
This vulnerability has been categorized under the ATT&CK framework as part of the credential access tactics, specifically targeting the use of stolen credentials for unauthorized access. The weakness creates opportunities for adversaries to perform credential dumping operations and subsequently leverage these credentials for network infiltration activities. The static key usage pattern also makes this vulnerability susceptible to attacks that exploit known plaintext or chosen plaintext scenarios, where attackers can use previously obtained information to derive encryption keys and decrypt stored credentials. Security practitioners should consider this vulnerability as a critical component in their threat modeling exercises and ensure appropriate compensating controls are implemented to protect against credential-based attacks.