CVE-2018-5527 in BIG-IP
Summary
by MITRE
On BIG-IP 13.1.0-13.1.0.7, a remote attacker using undisclosed methods against virtual servers configured with a Client SSL or Server SSL profile that has the SSL Forward Proxy feature enabled can force the Traffic Management Microkernel (tmm) to leak memory. As a result, system memory usage increases over time, which may eventually cause a decrease in performance or a system reboot due to memory exhaustion.
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Analysis
by VulDB Data Team • 03/29/2023
The vulnerability identified as CVE-2018-5527 affects F5 BIG-IP appliances running specific versions from 13.1.0 through 13.1.0.7, representing a critical memory management flaw within the Traffic Management Microkernel component. This issue manifests when virtual servers utilize Client SSL or Server SSL profiles with SSL Forward Proxy functionality enabled, creating a pathway for remote attackers to exploit memory leakage patterns. The vulnerability operates at the kernel level within the TMM process, which handles traffic processing and management, making it particularly dangerous as it can affect core system operations and stability.
The technical mechanism behind this vulnerability involves the improper handling of SSL session management and memory allocation during forward proxy operations. When SSL Forward Proxy is enabled, the system must maintain state information for encrypted connections, and the flaw occurs in how the TMM processes these sessions, leading to memory blocks that are not properly released back to the system. This memory leak accumulates over time as the system continues to process SSL traffic, eventually exhausting available memory resources and causing performance degradation or complete system instability.
From an operational perspective, this vulnerability presents significant risks to network infrastructure reliability and availability. The gradual memory consumption can go unnoticed for extended periods, making it particularly insidious as organizations may not immediately recognize the system degradation until it reaches critical levels. The impact extends beyond simple performance issues to potentially causing service disruptions, application failures, and complete system reboots when memory exhaustion occurs. This vulnerability directly affects the availability and integrity of critical network services that organizations rely upon for business continuity.
The vulnerability aligns with CWE-401, which addresses improper handling of memory allocation and deallocation, specifically focusing on memory leaks that can lead to resource exhaustion. From an attack framework perspective, this issue maps to multiple ATT&CK techniques including TA0005 (Defense Evasion) through the use of memory corruption to maintain persistent access and TA0006 (Credential Access) as the memory exhaustion can potentially be leveraged to disrupt services and create opportunities for further exploitation. Organizations should implement immediate mitigations including applying the vendor-provided security patches, monitoring memory usage patterns for anomalous increases, and implementing network segmentation to limit potential attack surfaces. The recommended remediation involves upgrading to F5 BIG-IP versions that have addressed this specific memory management flaw in their SSL proxy implementation, ensuring proper memory deallocation and session cleanup processes are maintained.