CVE-2018-15311 in BIG-IP
Summary
by MITRE
When F5 BIG-IP 13.0.0-13.1.0.5, 12.1.0-12.1.3.5, 11.6.0-11.6.3.2, or 11.5.1-11.5.6 is processing specially crafted TCP traffic with the Large Receive Offload (LRO) feature enabled, TMM may crash, leading to a failover event. This vulnerability is not exposed unless LRO is enabled, so most affected customers will be on 13.1.x. LRO has been available since 11.4.0 but is not enabled by default until 13.1.0.
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Analysis
by VulDB Data Team • 05/25/2023
This vulnerability affects F5 BIG-IP systems running specific versions where the Large Receive Offload feature creates a condition that allows specially crafted TCP traffic to cause the Traffic Management Microkernel (TMM) to crash. The flaw exists in the processing of network packets when LRO is enabled, which is a network optimization feature designed to reduce cpu overhead by allowing the network interface card to aggregate multiple received packets into a single larger packet. The vulnerability specifically targets versions 13.0.0 through 13.1.0.5, 12.1.0 through 12.1.3.5, 11.6.0 through 11.6.3.2, and 11.5.1 through 11.5.6, making it particularly relevant to users on version 13.1.x where LRO is enabled by default. The issue represents a denial of service condition that can trigger failover events in high availability configurations, potentially disrupting service availability and causing cascading failures in network infrastructure. This vulnerability aligns with CWE-121 which describes heap-based buffer overflow conditions and reflects the broader category of memory corruption vulnerabilities that can lead to system instability. The attack vector requires that the target system has LRO enabled, which means that most affected customers are likely to be those who have explicitly enabled this feature or are running the newer versions where it is enabled by default. The impact extends beyond simple service disruption as failover events can cause temporary loss of network connectivity and require manual intervention to restore normal operations. From a cybersecurity perspective, this vulnerability demonstrates how seemingly benign network optimization features can become attack vectors when not properly validated against malicious input patterns. The vulnerability's exploitation requires specific conditions including the presence of LRO and the injection of specially crafted TCP traffic, making it less likely to be exploited in the wild but still significant for organizations with exposed systems. Organizations using F5 BIG-IP systems should consider this vulnerability as part of their broader security posture assessment, particularly those with high availability configurations where failover events can have severe operational consequences. The vulnerability also relates to ATT&CK technique T1499 which covers network denial of service attacks and highlights the importance of network infrastructure hardening against crafted traffic patterns. Network administrators should review their current LRO configurations and consider disabling the feature if it is not essential for their operational requirements. The vulnerability serves as a reminder that network optimization features, while beneficial for performance, can introduce security risks when not properly tested against adversarial conditions. Organizations should implement monitoring to detect unusual failover patterns that might indicate exploitation attempts and maintain current threat intelligence to stay informed about similar vulnerabilities in network infrastructure components. The technical nature of the flaw suggests that it may be exploitable through carefully constructed network traffic that triggers memory corruption within the TMM process, potentially allowing attackers to cause service disruption while maintaining operational stealth. This vulnerability underscores the importance of comprehensive testing of network infrastructure components, particularly when implementing new features or optimization settings that could affect core system stability.