CVE-2016-7475 in BIG-IP
Summary
by MITRE
Under some circumstances on BIG-IP 12.0.0-12.1.0, 11.6.0-11.6.1, or 11.4.0-11.5.4 HF1, the Traffic Management Microkernel (TMM) may not properly clean-up pool member network connections when using SPDY or HTTP/2 virtual server profiles.
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Analysis
by VulDB Data Team • 05/23/2023
The vulnerability described in CVE-2016-7475 affects F5 BIG-IP appliances running specific versions of the Traffic Management Microkernel (TMM) component. This issue manifests when the system processes virtual server profiles that utilize SPDY or HTTP/2 protocols, creating a potential denial of service condition through improper connection management. The affected versions span multiple release lines including 12.0.0 through 12.1.0, 11.6.0 through 11.6.1, and 11.4.0 through 11.5.4 HF1, indicating a widespread impact across the F5 BIG-IP platform. The root cause lies in the TMM's failure to properly clean up network connections when these specific protocol profiles are employed, leading to resource exhaustion over time.
This vulnerability represents a classic case of resource leak or connection handling flaw that can be exploited to cause denial of service conditions. The technical implementation fails to properly manage the lifecycle of network connections established through SPDY or HTTP/2 virtual server profiles, resulting in persistent connections that consume system resources without proper cleanup. The flaw operates at the kernel level within the TMM component, making it particularly dangerous as it affects the core traffic management functionality of the appliance. According to CWE classification, this vulnerability maps to CWE-404, which describes improper resource cleanup or release, and CWE-122, which covers heap-based buffer overflow conditions. The operational impact extends beyond simple resource consumption as it can lead to complete service unavailability when connection pools become exhausted.
The operational implications of CVE-2016-7475 are significant for organizations relying on F5 BIG-IP appliances for their load balancing and traffic management needs. When exploited, the vulnerability can cause progressive degradation of service performance followed by complete service disruption, as the system's ability to establish new connections becomes compromised. This affects not only the availability of web applications but also impacts the overall network infrastructure reliability. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving resource exhaustion and denial of service, specifically mapping to T1499.004 for network denial of service and T1566.002 for phishing with malicious attachments, though the latter is more indirect as the vulnerability itself creates conditions for service disruption rather than being an attack vector directly. Organizations using affected F5 versions may experience cascading failures as connection exhaustion propagates through the system.
Mitigation strategies for CVE-2016-7475 should focus on immediate remediation through official F5 security patches and updates. Organizations must prioritize upgrading their BIG-IP appliances to versions that contain the necessary fixes for proper connection cleanup in SPDY and HTTP/2 profiles. Network administrators should implement monitoring solutions to detect abnormal connection patterns that may indicate exploitation attempts. The recommended approach includes applying the vendor-supplied security patches as soon as they become available, typically through F5's official support channels and security bulletins. Additionally, implementing connection rate limiting and monitoring for unusual connection behavior can provide early detection of potential exploitation. Organizations should also consider temporarily disabling SPDY or HTTP/2 profiles if immediate patching is not feasible, though this represents a temporary workaround rather than a permanent solution. The fix addresses the fundamental TMM connection management issue by ensuring proper cleanup of pool member network connections when these specific protocol profiles are utilized, thereby preventing the resource exhaustion condition that leads to service disruption.