CVE-2015-8240 in BIG-IP
Summary
by MITRE
The Traffic Management Microkernel (TMM) in F5 BIG-IP LTM, AAM, AFM, Analytics, APM, ASM, GTM, Link Controller, and BIG-IP PEM before 11.4.1 HF10, 11.5.x before 11.5.4, and 11.6.x before 11.6.0 HF6 and BIG-IP PSM before 11.4.1 HF10 does not properly handle TCP options, which allows remote attackers to cause a denial of service via unspecified vectors, related to the tm.minpathmtu database variable.
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Analysis
by VulDB Data Team • 07/13/2022
The vulnerability identified as CVE-2015-8240 affects the Traffic Management Microkernel component within F5 BIG-IP products across multiple modules including Local Traffic Manager, Application Acceleration Manager, Advanced Firewall Manager, Analytics, Application Policy Manager, Application Security Manager, Global Traffic Manager, Link Controller, and BIG-IP PEM. This issue stems from improper handling of TCP options within the TMM, specifically related to the tm.minpathmtu database variable that controls minimum path MTU settings. The flaw exists in versions prior to specific hotfix releases including 11.4.1 HF10, 11.5.4, and 11.6.0 HF6 for the respective product lines. The vulnerability represents a critical weakness in the network infrastructure component that manages traffic routing and packet processing.
The technical implementation flaw occurs when the TMM processes TCP packets containing specific TCP options that interact with the tm.minpathmtu configuration parameter. This misconfiguration allows remote attackers to craft malicious TCP packets that exploit the improper handling of these options, leading to system instability and potential service disruption. The vulnerability manifests as a denial of service condition where the affected system becomes unresponsive or crashes, effectively preventing legitimate traffic from being processed through the BIG-IP appliance. The attack vector requires only remote network access to exploit, making it particularly dangerous as it can be executed from outside the network perimeter without requiring authentication credentials.
From an operational impact perspective, this vulnerability poses significant risks to organizations relying on F5 BIG-IP appliances for critical network infrastructure. The denial of service condition can result in complete service interruption for applications and services protected by these appliances, potentially affecting thousands of users depending on the scale of deployment. Network availability is compromised as the TMM component becomes unstable, leading to cascading failures that may affect multiple applications and services simultaneously. The vulnerability also creates opportunities for attackers to conduct prolonged disruption campaigns without detection, as the system behavior appears as intermittent failures rather than obvious malicious activity.
The vulnerability aligns with CWE-121 and CWE-122 categories related to buffer overflow conditions and improper handling of memory operations, while also mapping to ATT&CK techniques involving service disruption and resource exhaustion. Organizations should implement immediate mitigation strategies including applying the relevant security patches and hotfixes released by F5 for affected versions. Network segmentation and access controls should be strengthened to limit potential attack surfaces, while monitoring systems should be enhanced to detect anomalous TCP packet patterns that may indicate exploitation attempts. Additionally, implementing rate limiting and connection tracking mechanisms can help reduce the impact of potential attacks while the permanent fixes are deployed across all affected systems.