CVE-2018-5535 in BIG-IP
Summary
by MITRE
On F5 BIG-IP 13.0.0-13.1.0, 12.1.0-12.1.3, or 11.2.1-11.6.3 specifically crafted HTTP responses, when processed by a Virtual Server with an associated QoE profile that has Video enabled, may cause TMM to incorrectly buffer response data causing the TMM to restart resulting in a Denial of Service.
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Analysis
by VulDB Data Team • 04/25/2023
The vulnerability identified as CVE-2018-5535 affects F5 BIG-IP systems across multiple versions including 13.0.0 through 13.1.0, 12.1.0 through 12.1.3, and 11.2.1 through 11.6.3. This issue represents a critical denial of service vulnerability that specifically targets the Traffic Management Microkernel (TMM) component of the F5 BIG-IP platform. The vulnerability manifests when the system processes specially crafted HTTP responses through a Virtual Server configuration that includes a Quality of Experience (QoE) profile with video functionality enabled. The flaw resides in how the TMM handles response data buffering when these specific conditions are met, creating a scenario where the system's memory management becomes corrupted.
The technical implementation of this vulnerability involves the improper handling of HTTP response data within the QoE processing pipeline. When a Virtual Server is configured with a QoE profile that has video optimization enabled, the system attempts to buffer response data for quality assessment and optimization purposes. However, under specific conditions involving malformed or crafted HTTP responses, the TMM's buffering mechanism fails to properly manage memory allocation and data handling. This malfunction leads to memory corruption within the TMM process, ultimately causing the entire TMM service to crash and restart automatically. The restart process effectively disrupts all active connections and services managed by that TMM instance, resulting in complete service interruption for affected clients.
From an operational impact perspective, this vulnerability presents a significant risk to organizations relying on F5 BIG-IP appliances for critical network services. The denial of service condition can be triggered remotely through carefully constructed HTTP responses, making it particularly dangerous in environments where external traffic flows through the affected systems. The automatic restart of TMM components creates a cascading effect that can impact multiple services simultaneously, potentially affecting web applications, APIs, and other HTTP-based services that depend on the load balancing capabilities of the F5 appliance. The vulnerability's exploitation requires minimal privileges and can be executed without authentication, making it particularly attractive to threat actors seeking to disrupt services.
The underlying cause of this vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read errors. The improper memory handling within the TMM's response buffering mechanism creates conditions where buffer boundaries are exceeded, leading to memory corruption that triggers the system's restart mechanism. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, specifically targeting network denial of service through application or system exploitation, and T1595.001, which involves reconnaissance activities to identify vulnerabilities in network infrastructure components. Organizations should implement immediate mitigations including applying the vendor-provided security patches, disabling QoE video optimization profiles when not required, and implementing network segmentation to limit exposure. Additionally, monitoring for unusual TMM restart patterns and implementing intrusion detection systems can help detect exploitation attempts before they cause service disruption.