CVE-2015-8099 in BIG-IP
Summary
by MITRE
F5 BIG-IP LTM, AFM, Analytics, APM, ASM, Link Controller, and PEM 11.3.x, 11.4.x before 11.4.1 HF10, 11.5.x before 11.5.4, 11.6.x before 11.6.1, and 12.x before 12.0.0 HF1; BIG-IP AAM 11.4.x before 11.4.1 HF10, 11.5.x before 11.5.4, 11.6.x before 11.6.1, and 12.x before 12.0.0 HF1; BIG-IP DNS 12.x before 12.0.0 HF1; BIG-IP Edge Gateway, WebAccelerator, and WOM 11.3.0; BIG-IP GTM 11.3.x, 11.4.x before 11.4.1 HF10, 11.5.x before 11.5.4, and 11.6.x before 11.6.1; BIG-IP PSM 11.3.x and 11.4.x before 11.4.1 HF10; Enterprise Manager 3.0.0 through 3.1.1; BIG-IQ Cloud and BIG-IQ Security 4.0.0 through 4.5.0; BIG-IQ Device 4.2.0 through 4.5.0; BIG-IQ ADC 4.5.0; BIG-IQ Centralized Management 4.6.0; and BIG-IQ Cloud and Orchestration 1.0.0 on the 3900, 6900, 8900, 8950, 11000, 11050, PB100 and PB200 platforms, when software SYN cookies are configured on virtual servers, allow remote attackers to cause a denial of service (High-Speed Bridge hang) via an invalid TCP segment.
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Analysis
by VulDB Data Team • 08/19/2022
This vulnerability affects multiple F5 BIG-IP product lines including Local Traffic Manager, Advanced Firewall Manager, Analytics, Application Persistence Manager, Application Security Manager, Link Controller, and PEM modules across various software versions. The flaw manifests when SYN cookies are enabled on virtual servers, creating a condition where remote attackers can exploit invalid TCP segments to trigger a denial of service attack resulting in High-Speed Bridge hang conditions. The vulnerability represents a critical weakness in the network stack processing logic of these security appliances, specifically impacting how they handle malformed TCP traffic when SYN cookie protection is active.
The technical implementation of this vulnerability stems from insufficient validation of TCP segment headers during the SYN cookie processing phase. When an attacker sends malformed TCP segments with invalid sequence numbers or unexpected flags, the system's High-Speed Bridge component becomes overwhelmed with processing these malformed packets, leading to system instability and complete service disruption. This behavior aligns with CWE-129, which describes improper validation of input boundaries, and CWE-400, which covers resource exhaustion vulnerabilities. The attack vector requires only remote access to the network and does not require authentication, making it particularly dangerous in production environments where these appliances serve as critical infrastructure components.
The operational impact of this vulnerability extends beyond simple service interruption, as it affects core network infrastructure components that typically operate with high availability requirements. When the High-Speed Bridge hangs, it impacts the entire appliance's ability to process network traffic, potentially affecting thousands of concurrent connections across multiple virtual servers. This vulnerability can be exploited by attackers to disrupt critical business services, particularly in environments where F5 appliances protect web applications, load balancing services, or security perimeters. The attack can be executed from any location with network connectivity to the vulnerable appliance, making it a significant threat to organizations relying on these platforms for network security and traffic management.
Organizations should immediately implement mitigations including upgrading to patched versions of affected software releases, disabling SYN cookies on virtual servers if not required for security, and implementing network segmentation to limit attack surface exposure. The recommended remediation strategy involves applying the vendor-provided hotfixes for each affected product line, particularly focusing on versions prior to the specified patch levels including 11.4.1 HF10, 11.5.4, 11.6.1, and 12.0.0 HF1. Network administrators should also consider implementing intrusion detection systems to monitor for suspicious TCP segment patterns and establish monitoring procedures to detect early signs of exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to T1499.004 for network denial of service and T1071.004 for application layer protocol usage, representing a significant threat to network infrastructure security.