CVE-2018-0297 in Firepower Threat Defense
Summary
by MITRE
A vulnerability in the detection engine of Cisco Firepower Threat Defense software could allow an unauthenticated, remote attacker to bypass a configured Secure Sockets Layer (SSL) Access Control (AC) policy to block SSL traffic. The vulnerability is due to the incorrect handling of TCP SSL packets received out of order. An attacker could exploit this vulnerability by sending a crafted SSL connection through the affected device. A successful exploit could allow the attacker to bypass a configured SSL AC policy to block SSL traffic. Cisco Bug IDs: CSCvg09316.
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Analysis
by VulDB Data Team • 02/06/2020
The vulnerability described in CVE-2018-0297 represents a critical flaw in Cisco Firepower Threat Defense software that undermines the integrity of SSL traffic filtering mechanisms. This issue specifically affects the detection engine's ability to properly process TCP SSL packets that arrive in an incorrect sequence, creating a pathway for attackers to circumvent security policies designed to block SSL traffic. The vulnerability stems from improper state management within the SSL inspection process, where the system fails to correctly handle packet reordering that occurs naturally in network communications. Such packet reordering is a common occurrence in TCP/IP networks due to varying network paths and routing decisions, making this a particularly insidious weakness that could be exploited in real-world scenarios.
The technical exploitation of this vulnerability requires an attacker to craft and transmit specifically formatted SSL connection packets that arrive out of order at the affected Firepower device. This particular flaw operates at the network protocol level, targeting the SSL inspection engine's packet processing logic rather than higher-level application vulnerabilities. The vulnerability is classified under CWE-129 as an "Improper Validation of Array Index" and relates to improper handling of out-of-order data sequences, which is a well-documented weakness in network protocol implementations. When SSL packets arrive in unexpected order, the detection engine fails to properly validate the packet sequence and may incorrectly process the connection state, leading to bypass of configured access control policies. This represents a fundamental failure in the SSL inspection engine's ability to maintain proper connection state tracking and validation.
From an operational impact perspective, this vulnerability creates a significant security risk for organizations relying on Cisco Firepower devices for SSL traffic filtering and monitoring. The ability to bypass SSL access control policies means that malicious traffic that should be blocked according to configured security policies can potentially pass through the firewall undetected. This could enable attackers to establish unauthorized connections, exfiltrate data, or gain access to internal network resources that would normally be restricted by SSL filtering policies. The remote and unauthenticated nature of the exploit means that attackers do not require valid credentials or physical access to the network to exploit this vulnerability, making it particularly dangerous in environments where network monitoring and control are critical for security. The vulnerability essentially allows for a complete bypass of SSL policy enforcement, potentially undermining the entire security posture of organizations relying on the affected Cisco Firepower devices.
Organizations should immediately implement mitigations including applying the relevant Cisco security patches and updates to address the root cause of the vulnerability. Network administrators should also consider implementing additional monitoring and logging mechanisms to detect potential exploitation attempts, as the vulnerability may not produce obvious signs of compromise. The remediation process should include thorough testing of the updated software in non-production environments before deployment to ensure that the patches do not introduce any operational issues or regressions in network functionality. Additionally, organizations should review their existing SSL inspection policies and ensure that multiple layers of security controls are in place to provide defense in depth. From an ATT&CK framework perspective, this vulnerability aligns with techniques such as T1071.004 for Application Layer Protocol: DNS and T1566 for Credential Access, as it allows for bypassing network controls that would normally prevent unauthorized access to network resources through SSL traffic. The vulnerability demonstrates how protocol-level weaknesses can create fundamental security gaps that affect the entire network security architecture, emphasizing the importance of proper protocol implementation and validation in security-critical systems.