CVE-2016-7468 in BIG-IP
Summary
by MITRE
An unauthenticated remote attacker may be able to disrupt services on F5 BIG-IP 11.4.1 - 11.5.4 devices with maliciously crafted network traffic. This vulnerability affects virtual servers associated with TCP profiles when the BIG-IP system's tm.tcpprogressive db variable value is set to non-default setting "enabled". The default value for the tm.tcpprogressive db variable is "negotiate". An attacker may be able to disrupt traffic or cause the BIG-IP system to fail over to another device in the device group.
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Analysis
by VulDB Data Team • 09/19/2024
The vulnerability described in CVE-2016-7468 represents a significant security flaw in F5 BIG-IP load balancing appliances that can lead to service disruption and potential system failure. This weakness specifically targets devices running F5 BIG-IP versions 11.4.1 through 11.5.4, where the tm.tcpprogressive database variable is configured to "enabled" rather than the default "negotiate" setting. The flaw operates at the network protocol level, exploiting how the system handles TCP traffic processing and can be exploited by unauthenticated remote attackers without requiring any credentials or prior access to the system. This makes the vulnerability particularly dangerous as it can be leveraged by anyone with network access to the affected devices.
The technical implementation of this vulnerability stems from improper handling of TCP progressive processing when the tm.tcpprogressive variable is enabled. When configured to "enabled", the BIG-IP system attempts to optimize TCP traffic handling through progressive processing techniques that can become unstable when processing malformed or malicious network packets. The vulnerability specifically impacts virtual servers that utilize TCP profiles, creating a condition where crafted network traffic can cause the system to enter an unstable state. This progressive TCP processing feature, designed to improve performance by dynamically adjusting TCP parameters, becomes a vector for denial of service when exploited through carefully constructed packets that trigger memory corruption or resource exhaustion conditions within the system's TCP stack implementation.
The operational impact of this vulnerability extends beyond simple service disruption to potentially cause complete system failure or failover events within device groups. When successfully exploited, the malicious traffic can cause the BIG-IP system to become unresponsive, leading to service interruption for all applications and users relying on that particular device. The vulnerability's potential to trigger failover operations within device groups creates additional operational concerns, as it can cause unnecessary switchover events that disrupt service continuity and can overwhelm backup systems with sudden traffic spikes. Organizations using F5 BIG-IP appliances in mission-critical environments face significant risk of service degradation or complete outages when this vulnerability is exploited, particularly in scenarios where failover mechanisms are configured to activate automatically upon system instability.
Security professionals should consider this vulnerability in the context of the ATT&CK framework's privilege escalation and denial of service tactics, as it enables remote attackers to compromise system availability without requiring elevated privileges. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, though the specific implementation appears to involve memory management issues within TCP processing rather than traditional buffer overflows. Organizations should immediately implement mitigation strategies including disabling the tm.tcpprogressive feature when not required, applying official F5 security patches, and implementing network segmentation to limit access to affected systems. Additionally, monitoring for unusual traffic patterns and implementing intrusion detection systems can help identify exploitation attempts before they cause significant damage to service availability.
The vulnerability demonstrates the critical importance of proper configuration management in network infrastructure devices, as the default setting of "negotiate" provides adequate protection while the "enabled" setting introduces unnecessary risk. Organizations should conduct comprehensive audits of their F5 BIG-IP configurations to identify all systems with the problematic tm.tcpprogressive setting and ensure that only necessary services have access to these vulnerable configurations. Regular security assessments and vulnerability scanning should include verification of database variable settings to prevent configuration drift that could expose systems to this and similar vulnerabilities. The incident underscores the need for robust change management processes that prevent unauthorized modifications to critical system parameters that could introduce security weaknesses into operational environments.