CVE-2018-5536 in BIG-IP APM
Summary
by MITRE
A remote attacker via undisclosed measures, may be able to exploit an F5 BIG-IP APM 13.0.0-13.1.0.7 or 12.1.0-12.1.3.5 virtual server configured with an APM per-request policy object and cause a memory leak in the APM module.
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Analysis
by VulDB Data Team • 04/25/2023
The vulnerability identified as CVE-2018-5536 represents a critical memory management issue within F5 BIG-IP Access Policy Manager (APM) module affecting specific versions of the F5 BIG-IP platform. This flaw manifests when virtual servers are configured with APM per-request policy objects, creating a condition where malicious actors can trigger systematic memory consumption that ultimately leads to service degradation or complete system unavailability. The vulnerability operates at the application layer and specifically targets the APM module's handling of memory allocation and deallocation processes during policy evaluation.
The technical implementation of this vulnerability stems from improper memory management within the APM module's per-request policy processing mechanism. When a virtual server processes requests through APM per-request policy objects, the system fails to properly release allocated memory resources after policy evaluation completes. This memory leak occurs incrementally with each processed request, gradually consuming available system memory until the platform reaches critical resource exhaustion levels. The vulnerability is particularly concerning because it operates silently, allowing attackers to consume system resources without generating obvious network anomalies or alerts that would typically trigger intrusion detection systems.
From an operational perspective, this vulnerability presents significant risk to enterprise environments relying on F5 BIG-IP APM for access control and application delivery. The memory leak can be exploited remotely through legitimate network traffic, making it particularly dangerous as it does not require authentication or specialized access privileges. The impact extends beyond simple performance degradation to potentially causing complete service outages, especially in high-traffic environments where the memory consumption accelerates rapidly. Organizations may experience unexpected application failures, increased latency, and system instability that can affect business continuity and user experience across critical applications protected by the affected BIG-IP appliances.
The vulnerability aligns with CWE-401, which specifically addresses improper handling of memory allocation and deallocation, and demonstrates characteristics consistent with the ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion. Organizations should implement immediate mitigation strategies including applying the vendor-provided security patches, monitoring system memory consumption patterns for unusual increases, and implementing network segmentation to limit potential attack vectors. Additionally, administrators should consider temporary workarounds such as disabling per-request policy objects or implementing rate limiting mechanisms to reduce the attack surface. The vulnerability underscores the importance of maintaining current security patches and conducting regular vulnerability assessments to identify and remediate similar memory management flaws in critical infrastructure components.