CVE-2015-1569 in FortiClient
Summary
by MITRE
Fortinet FortiClient 5.2.028 for iOS does not validate certificates, which makes it easier for man-in-the-middle attackers to spoof SSL VPN servers via a crafted certificate.
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Analysis
by VulDB Data Team • 04/10/2018
The vulnerability identified as CVE-2015-1569 affects Fortinet FortiClient version 5.2.028 on iOS devices, representing a critical security flaw in the mobile VPN client's certificate validation mechanism. This issue stems from insufficient certificate verification processes that fail to properly validate the authenticity and integrity of SSL certificates presented by VPN servers. The flaw creates a significant security gap that allows malicious actors to exploit the trust relationship between the mobile client and enterprise VPN infrastructure.
The technical implementation of this vulnerability lies in the absence of proper certificate chain validation within the iOS FortiClient application. When establishing SSL VPN connections, the application should verify certificate signatures against trusted certificate authorities and ensure proper certificate expiration dates, subject names, and other security attributes. However, the vulnerable version fails to perform these essential validation steps, enabling attackers to present forged certificates that appear legitimate to the client. This weakness directly relates to CWE-295, which addresses improper certificate validation, and represents a fundamental failure in the application's security architecture.
The operational impact of this vulnerability is severe for organizations relying on FortiClient for mobile VPN access. Man-in-the-middle attackers can exploit this flaw to intercept, modify, or redirect encrypted communications between mobile users and corporate VPN servers. This compromise enables unauthorized access to sensitive corporate data, potential credential theft, and complete network infiltration. The vulnerability is particularly dangerous in environments where mobile workers access confidential information, as it undermines the entire purpose of SSL/TLS encryption and VPN security. Attackers can create convincing fake VPN server certificates that bypass the client's validation checks, making the attack difficult to detect and trace.
Organizations should immediately implement multiple layers of mitigation strategies to address this vulnerability. The primary recommendation involves updating to the latest version of FortiClient that includes proper certificate validation mechanisms, which aligns with ATT&CK technique T1071.004 for application layer protocol usage. Additionally, network administrators should implement additional security controls such as certificate pinning, enhanced monitoring of VPN connections, and regular security audits of mobile device configurations. The remediation process should include comprehensive testing to ensure that certificate validation works correctly after updates, and organizations should consider implementing network segmentation to limit the potential impact of successful attacks. This vulnerability demonstrates the critical importance of proper certificate validation in mobile security solutions and serves as a reminder of the necessity for robust cryptographic implementation in enterprise mobile applications.