CVE-2019-6671 in BIG-IP
Summary
by MITRE
On BIG-IP 15.0.0-15.0.1, 14.1.0-14.1.2, 14.0.0-14.0.1, and 13.1.0-13.1.3.1, under certain conditions tmm may leak memory when processing packet fragments, leading to resource starvation.
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Analysis
by VulDB Data Team • 03/05/2024
The vulnerability identified as CVE-2019-6671 affects F5 BIG-IP appliances across multiple version ranges including 15.0.0-15.0.1, 14.1.0-14.1.2, 14.0.0-14.0.1, and 13.1.0-13.1.3.1. This issue resides within the traffic management module tmm which is responsible for processing network packets and managing traffic flow. The flaw manifests when the system encounters specific packet fragmentation scenarios that trigger improper memory handling within the tmm process. This memory management deficiency represents a critical security weakness that can be exploited to disrupt normal system operations through resource exhaustion.
The technical implementation of this vulnerability involves memory leak conditions occurring during packet fragment processing within the tmm component. When the system processes fragmented network packets under certain circumstances, the memory allocated for handling these fragments is not properly released back to the system. This results in gradual memory consumption over time as the system continues to process incoming traffic. The vulnerability specifically affects the way the tmm module handles packet reassembly and memory allocation for fragmented data, creating a condition where allocated memory blocks remain occupied indefinitely. This behavior aligns with CWE-401, which describes improper handling of memory allocation and deallocation leading to memory leaks.
The operational impact of CVE-2019-6671 extends beyond simple performance degradation to potentially complete system compromise. As memory consumption increases gradually through repeated packet fragment processing, the system eventually reaches a state of resource starvation where critical services become unavailable. This condition can lead to denial of service scenarios affecting all network services managed by the BIG-IP appliance. The vulnerability's exploitation requires only normal network traffic patterns to trigger the memory leak, making it particularly dangerous as it can be activated through routine network operations without requiring specialized attack vectors. The resource starvation effect can be amplified by sustained network traffic, making this vulnerability particularly concerning for high-traffic environments where the appliance handles significant packet processing loads.
Mitigation strategies for this vulnerability should prioritize immediate patch application from F5 as the primary remediation approach. Organizations must ensure all affected BIG-IP versions are updated to patched releases that address the memory management flaw in the tmm module. Network administrators should also implement monitoring solutions to track memory consumption patterns and identify potential exploitation attempts through unusual memory usage trends. Additionally, implementing traffic rate limiting and packet filtering rules can help reduce the exposure window by limiting the volume of fragmented packets processed by the affected system. The vulnerability's characteristics align with ATT&CK technique T1499 which involves resource exhaustion attacks, making defensive measures that monitor resource consumption particularly valuable for early detection and response. System administrators should also consider implementing redundant systems or failover mechanisms to maintain service availability during patch deployment windows.