CVE-2016-6396 in FireSIGHT
Summary
by MITRE
Cisco Firepower Management Center before 6.1 and FireSIGHT System Software before 6.1, when certain malware blocking options are enabled, allow remote attackers to bypass malware detection via crafted fields in HTTP headers, aka Bug ID CSCuz44482.
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Analysis
by VulDB Data Team • 04/14/2019
The vulnerability described in CVE-2016-6396 represents a significant security flaw in Cisco Firepower Management Center and FireSIGHT System Software versions prior to 6.1. This issue affects organizations that rely on Cisco's next-generation firewall and intrusion prevention capabilities for malware detection and blocking. The vulnerability specifically manifests when certain malware blocking options are enabled, creating a bypass mechanism that allows remote attackers to evade detection of malicious content. The flaw is particularly concerning as it operates at the HTTP protocol level, where attackers can manipulate header fields to circumvent security controls that should be protecting network endpoints.
The technical implementation of this vulnerability stems from insufficient validation of HTTP header fields within the malware detection engine. When malware blocking features are enabled, the system should rigorously inspect all incoming HTTP traffic to identify and block malicious content. However, the flaw allows attackers to craft HTTP headers with specific field values that bypass the detection logic. This occurs because the malware detection system fails to properly normalize or validate header field contents, enabling crafted inputs to slip through security controls that should prevent their execution. The vulnerability is classified as a bypass weakness that operates at the application layer of the network stack, specifically affecting the HTTP protocol handling capabilities of the security appliance.
The operational impact of this vulnerability is substantial for organizations using affected Cisco Firepower systems. Attackers can exploit this weakness to deliver malware payloads that would otherwise be detected and blocked by the security infrastructure. This creates a false sense of security for network defenders who rely on the system's malware blocking capabilities. The remote nature of the attack means that threat actors can exploit this vulnerability from outside the network perimeter without requiring physical access or local credentials. The bypass affects the core functionality of the malware detection system, potentially allowing persistent threats, zero-day exploits, and other malicious payloads to reach target systems undetected. This vulnerability directly impacts the CIA triad by weakening confidentiality and integrity protections within the network security infrastructure.
Organizations should prioritize immediate remediation by upgrading to Cisco Firepower Management Center 6.1 or later versions and FireSIGHT System Software 6.1 or later. The vulnerability aligns with CWE-20, which describes improper input validation, and represents a classic case of insufficient sanitization of user-supplied data within security controls. From an ATT&CK framework perspective, this vulnerability maps to technique T1071.004 for application layer protocol traffic shaping and T1059 for command and scripting interpreter usage. Network defenders should implement additional monitoring for suspicious HTTP header patterns and consider deploying complementary security controls such as web application firewalls and network traffic analysis tools. The remediation process should include thorough testing of updated firmware to ensure compatibility with existing network configurations while maintaining security posture. Organizations should also conduct vulnerability assessments to identify any potential exploitation attempts that may have occurred prior to the patch deployment.