CVE-2017-6632 in Firepower System Software
Summary
by MITRE
A vulnerability in the logging configuration of Secure Sockets Layer (SSL) policies for Cisco FirePOWER System Software 5.3.0 through 6.2.2 could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition due to high consumption of system resources. The vulnerability is due to the logging of certain TCP packets by the affected software. An attacker could exploit this vulnerability by sending a flood of crafted TCP packets to an affected device. A successful exploit could allow the attacker to cause a DoS condition. The success of an exploit is dependent on how an administrator has configured logging for SSL policies for a device. This vulnerability affects Cisco FirePOWER System Software that is configured to log connections by using SSL policy default actions. Cisco Bug IDs: CSCvd07072.
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Analysis
by VulDB Data Team • 05/22/2017
The vulnerability described in CVE-2017-6632 represents a significant denial of service weakness within Cisco FirePOWER System Software versions 5.3.0 through 6.2.2. This flaw specifically targets the logging mechanisms associated with Secure Sockets Layer policies, creating a scenario where an unauthenticated remote attacker can exploit the system's resource consumption patterns to disrupt normal operations. The vulnerability stems from the software's handling of TCP packet logging within SSL policy contexts, where certain packet types trigger excessive logging behavior that gradually depletes system resources.
The technical exploitation mechanism relies on sending a flood of crafted TCP packets to the affected device, which triggers the problematic logging behavior in the SSL policy processing module. When the system processes these packets through its default SSL policy actions, it enters a resource-intensive logging loop that consumes CPU cycles and memory resources at an unsustainable rate. This behavior creates a cascading effect where legitimate network traffic becomes increasingly difficult to process as system resources become consumed by the logging overhead. The vulnerability's exploitability is directly tied to the administrator's logging configuration choices, particularly when default SSL policy actions are configured to log connections, making the impact highly dependent on deployment-specific settings.
From an operational impact perspective, this vulnerability presents a severe risk to network availability and business continuity. The DoS condition can effectively render the FirePOWER device non-functional, disrupting network security monitoring and traffic inspection capabilities that organizations rely upon for threat detection. The attack requires minimal privileges and can be executed from remote locations, making it particularly dangerous in production environments where such devices often serve as critical security infrastructure components. The resource exhaustion occurs gradually but consistently, potentially allowing attackers to maintain their disruptive influence without detection, as the system may not immediately show signs of compromise.
Organizations affected by this vulnerability should implement immediate mitigations including modifying SSL policy configurations to reduce logging intensity, implementing rate limiting controls on TCP packet processing, and establishing monitoring protocols to detect unusual resource consumption patterns. The remediation process requires careful consideration of existing security policies to balance the need for logging with the risk of resource exhaustion. System administrators should also review and test SSL policy configurations in non-production environments before applying changes to production systems, ensuring that logging requirements for threat detection are maintained while preventing the vulnerable behavior patterns. This vulnerability aligns with CWE-400, which addresses improper resource management, and demonstrates characteristics consistent with attack patterns categorized under the MITRE ATT&CK framework's privilege escalation and denial of service tactics.