CVE-2017-6625 in Firepower Threat Defense
Summary
by MITRE
A "Cisco Firepower Threat Defense 6.0.0 through 6.2.2 and Cisco ASA with FirePOWER Module Denial of Service" vulnerability in the access control policy of Cisco Firepower System Software could allow an authenticated, remote attacker to cause an affected system to stop inspecting and processing packets, resulting in a denial of service (DoS) condition. The vulnerability is due to improper SSL policy handling by the affected software when packets are passed through the sensing interfaces of an affected system. An attacker could exploit this vulnerability by sending crafted packets through a targeted system. This vulnerability affects Cisco Firepower System Software that is configured with the SSL policy feature. Cisco Bug IDs: CSCvc84361.
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Analysis
by VulDB Data Team • 12/22/2020
The vulnerability described in CVE-2017-6625 represents a critical denial of service weakness affecting Cisco Firepower Threat Defense systems operating within version ranges 6.0.0 through 6.2.2, as well as Cisco ASA devices equipped with the FirePOWER module. This flaw specifically targets the access control policy implementation within the Cisco Firepower System Software, creating a scenario where authenticated remote attackers can manipulate system behavior to disrupt network traffic inspection processes. The vulnerability stems from inadequate handling of SSL policies within the sensing interfaces, which are critical components responsible for monitoring and analyzing network packets for security threats. When exploited, this weakness allows attackers to send specifically crafted packets that trigger the system's failure to process subsequent network traffic, effectively rendering the security appliance ineffective in its primary function of network protection.
The technical mechanism underlying this vulnerability involves the improper processing of SSL policy configurations within the Firepower system's packet inspection engine. When packets flow through the sensing interfaces of affected systems, the software fails to correctly manage the SSL policy enforcement logic, leading to a cascade of failures in the packet processing pipeline. This malfunction causes the system to enter a degraded state where it ceases to analyze and filter network traffic, creating a complete denial of service condition that impacts network availability and security monitoring capabilities. The vulnerability specifically affects systems configured with SSL policy features, which are commonly deployed in enterprise environments to monitor encrypted traffic for security threats. The flaw demonstrates poor input validation and error handling within the SSL policy processing module, as outlined in CWE-248, where an exception is thrown for an unspecified reason, leading to the system's inability to continue normal operations.
The operational impact of this vulnerability extends beyond simple service interruption to compromise the fundamental security posture of networks relying on Cisco Firepower appliances. Organizations utilizing these systems face significant risk of network disruption during attack windows, as the affected appliances become incapable of performing their core security functions including intrusion detection, malware prevention, and traffic filtering. The authenticated nature of the attack means that adversaries with valid credentials can exploit this weakness, potentially allowing for targeted disruption of security infrastructure without requiring advanced technical skills or specialized equipment. This vulnerability directly impacts the availability component of the CIA triad, as it prevents legitimate network traffic from being properly inspected and processed, effectively creating a security gap that could be exploited by malicious actors. The attack vector through sensing interfaces means that even systems with proper network segmentation could be compromised if attackers gain access to the network monitoring points where these appliances are deployed.
Mitigation strategies for CVE-2017-6625 should prioritize immediate system updates to the latest available software versions that contain patches addressing the SSL policy handling flaw. Cisco released specific patches for this vulnerability under bug ID CSCvc84361, and organizations should implement these updates as a priority measure to restore proper SSL policy functionality. Network administrators should also consider implementing additional monitoring and alerting mechanisms to detect potential exploitation attempts, as the vulnerability may manifest through unusual traffic patterns or system behavior that could indicate an active attack. The remediation process should include thorough testing of updated firmware in controlled environments before deployment to production systems to ensure compatibility with existing network configurations. Organizations should also review their access control policies to minimize the risk of unauthorized authentication, as the vulnerability requires authenticated access to exploit. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving denial of service and system compromise, potentially enabling further attacks through the disruption of network security monitoring capabilities. The vulnerability highlights the importance of proper SSL/TLS policy implementation and the need for robust error handling in security appliances to prevent single points of failure that could compromise entire network security infrastructures.