CVE-2016-6439 in ASA
Summary
by MITRE
A vulnerability in the detection engine reassembly of HTTP packets for Cisco Firepower System Software before 6.0.1 could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition due to the Snort process unexpectedly restarting. The vulnerability is due to improper handling of an HTTP packet stream. An attacker could exploit this vulnerability by sending a crafted HTTP packet stream to the detection engine on the targeted device. An exploit could allow the attacker to cause a DoS condition if the Snort process restarts and traffic inspection is bypassed or traffic is dropped.
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Analysis
by VulDB Data Team • 11/26/2024
The vulnerability identified as CVE-2016-6439 represents a critical flaw in Cisco Firepower System Software that affects versions prior to 6.0.1, specifically targeting the detection engine's HTTP packet reassembly functionality. This weakness resides within the Snort-based intrusion detection system component that processes and inspects network traffic for security threats. The vulnerability stems from inadequate handling of HTTP packet streams during the reassembly process, creating a condition where malformed or specially crafted HTTP traffic can trigger unexpected behavior in the system's core detection mechanisms.
The technical exploitation of this vulnerability occurs through the manipulation of HTTP packet streams that traverse the Firepower device's detection engine. When an attacker sends specifically crafted HTTP packets designed to exploit the improper reassembly logic, the Snort process experiences an unexpected restart condition. This restart represents a fundamental failure in the system's error handling and resource management capabilities, as the detection engine fails to properly validate or sanitize incoming HTTP traffic before processing it. The vulnerability operates at the protocol level where HTTP packets are fragmented and reassembled, creating a scenario where the reassembly logic encounters data structures it cannot properly handle, leading to process termination.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire security posture of the network infrastructure protected by the affected Firepower device. When the Snort process restarts due to the exploitation, the device enters a state where traffic inspection capabilities are temporarily bypassed or significantly degraded, leaving the network vulnerable to attacks that would normally be detected and blocked. This creates a window of opportunity for attackers to conduct further malicious activities without detection, as the device's primary security functions are temporarily disabled. The DoS condition effectively neutralizes the device's ability to perform its core security functions, potentially allowing attackers to establish persistent access to the network.
The vulnerability aligns with CWE-129, which addresses issues related to improper handling of input validation and processing, specifically in the context of protocol parsing and reassembly. From an adversarial perspective, this weakness maps to several ATT&CK techniques including T1498 for network denial of service and T1071 for application layer protocol usage. Organizations implementing Cisco Firepower systems must consider this vulnerability as part of their broader security risk assessment, particularly in environments where network availability and consistent security monitoring are critical. The remediation approach requires immediate deployment of Cisco's security patches and updates to version 6.0.1 or later, along with comprehensive network monitoring to detect potential exploitation attempts and ensure proper system recovery procedures are in place to minimize service disruption during patch deployment.