CVE-2016-8495 in FortiManager
Summary
by MITRE
FortiManager does not properly validate TLS certificates when probing for devices to administer. This leads to potential pre-shared secret exposure.
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Analysis
by VulDB Data Team • 11/14/2022
The vulnerability identified as CVE-2016-8495 affects FortiManager systems which are network security appliances designed to manage multiple Fortinet firewalls and other network devices from a centralized location. This weakness specifically resides in the certificate validation process during device probing operations where the system fails to properly verify the authenticity of Transport Layer Security certificates presented by target devices. The flaw occurs when FortiManager attempts to discover and establish connections with network devices through automated probing mechanisms that rely on TLS encryption protocols for secure communication. During these probing activities, the system should validate certificate chains and ensure that the presented certificates are issued by trusted Certificate Authorities and have not been tampered with or are not expired. However, the vulnerability allows attackers to potentially bypass these validation checks and establish connections with malicious devices or intercept communications.
The technical implementation of this vulnerability stems from inadequate certificate validation logic within FortiManager's device discovery and management protocols. When the system performs automated device probing, it should enforce strict certificate validation procedures that align with industry standards such as those defined in the Transport Layer Security RFC specifications. The flaw permits the acceptance of self-signed certificates, certificates from untrusted CAs, or certificates that have been modified in transit without proper cryptographic verification. This weakness creates a potential attack vector where an adversary could position a malicious device or intermediate system that presents a forged certificate during the probing process. The system's failure to validate certificate signatures, expiration dates, and certificate authority chains means that it may accept certificates that should be rejected based on standard security practices.
The operational impact of this vulnerability is significant as it directly threatens the confidentiality and integrity of administrative communications within network security environments. When pre-shared secrets are exposed due to improper certificate validation, attackers can potentially gain unauthorized access to network management systems and subsequently compromise the entire network infrastructure. The exposure of these secrets could allow malicious actors to establish persistent access to network devices, modify firewall rules, intercept traffic, or conduct man-in-the-middle attacks against legitimate management sessions. This vulnerability particularly affects organizations that rely on centralized network management solutions where FortiManager serves as the primary administrative interface for multiple security devices. The risk is compounded by the fact that the probing mechanism is often automated and continuously active, providing multiple opportunities for exploitation.
Organizations should implement several mitigation strategies to address this vulnerability effectively. Immediate remediation involves applying the latest security patches and firmware updates provided by Fortinet to correct the certificate validation logic. Network administrators should also implement additional monitoring and logging mechanisms to detect unusual device probing activities or certificate-related anomalies in network traffic. The implementation of certificate pinning techniques can provide an additional layer of protection by ensuring that only specific, pre-approved certificates are accepted for device authentication purposes. Security teams should also review and strengthen their overall certificate management practices, ensuring that all devices within the network environment maintain valid, properly issued certificates from trusted authorities. According to the CWE catalog, this vulnerability relates to CWE-295 which specifically addresses "Improper Certificate Validation" and aligns with ATT&CK technique T1566 which covers "Phishing" and related social engineering attacks that may exploit weak certificate validation mechanisms. The vulnerability also corresponds to the broader ATT&CK tactic of privilege escalation through compromised administrative credentials and network access. Organizations should conduct comprehensive security assessments to identify all instances of FortiManager systems within their environment and ensure that all instances have been properly updated and configured to prevent exploitation of this weakness.