CVE-2016-5023 in BIG-IP
Summary
by MITRE
Virtual servers in F5 BIG-IP systems 11.2.1 HF11 through HF15, 11.4.1 HF4 through HF10, 11.5.3 through 11.5.4, 11.6.0 HF5 through HF7, and 12.0.0, when configured with a TCP profile, allow remote attackers to cause a denial of service (Traffic Management Microkernel restart) via crafted network traffic.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 09/13/2022
The vulnerability identified as CVE-2016-5023 represents a critical denial of service weakness within F5 BIG-IP systems that affects multiple software versions including 11.2.1 through 11.5.4, 11.6.0 through 11.6.7, and 12.0.0. This flaw specifically manifests when virtual servers are configured with TCP profiles, creating a pathway for remote attackers to exploit the system's Traffic Management Microkernel component. The vulnerability falls under the category of improper handling of malformed input as classified by CWE-248, where the system fails to properly validate or process incoming network packets that contain crafted payloads designed to trigger system instability.
The technical exploitation of this vulnerability occurs through the manipulation of TCP traffic that is processed by the BIG-IP system's Traffic Management Microkernel. When properly crafted network packets are sent to virtual servers configured with TCP profiles, these packets trigger an internal error condition that results in the microkernel restarting. This restart process effectively disrupts all network services managed by the affected virtual servers, causing complete service interruption for all connected clients. The flaw demonstrates characteristics of a resource exhaustion attack pattern where the system's processing capabilities are overwhelmed by malformed input, leading to the kernel-level restart that terminates all active connections and service operations.
From an operational impact perspective, this vulnerability presents a severe risk to organizations relying on F5 BIG-IP systems for critical network infrastructure services. The remote nature of the attack means that adversaries can exploit this weakness from outside the network perimeter without requiring physical access or authentication credentials. The resulting traffic management microkernel restart creates cascading effects throughout the network infrastructure, potentially affecting multiple services and applications that depend on the affected BIG-IP system for load balancing, traffic routing, and application delivery. Organizations may experience extended downtime while the system recovers from the restart, potentially leading to business disruption and service level agreement violations.
The attack vector for CVE-2016-5023 aligns with techniques described in the MITRE ATT&CK framework under the T1499.004 sub-technique for Network Denial of Service, where adversaries leverage system vulnerabilities to disrupt network services. This vulnerability also corresponds to CWE-400, which addresses improper handling of resources, and CWE-772, relating to missing release of resource after effective lifetime, indicating that the system fails to properly manage and recover from malformed input conditions. Organizations should implement immediate mitigations including applying the vendor-provided security patches, configuring network access controls to limit exposure, and implementing monitoring solutions to detect anomalous traffic patterns that may indicate exploitation attempts. Additionally, network segmentation strategies should be employed to reduce the attack surface and limit the potential impact of successful exploitation attempts against the affected systems.