CVE-2018-5517 in BIG-IP
Summary
by MITRE
On F5 BIG-IP 13.1.0-13.1.0.5, malformed TCP packets sent to a self IP address or a FastL4 virtual server may cause an interruption of service. The control plane is not exposed to this issue. This issue impacts the data plane virtual servers and self IPs.
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Analysis
by VulDB Data Team • 03/08/2023
The vulnerability identified as CVE-2018-5517 represents a critical denial-of-service weakness affecting F5 BIG-IP systems running version 13.1.0 through 13.1.0.5. This flaw specifically targets the data plane components of the F5 BIG-IP platform, particularly impacting FastL4 virtual servers and self IP addresses. The vulnerability demonstrates characteristics consistent with a buffer overflow or parsing error in the TCP packet processing module, where malformed network traffic can trigger unexpected behavior in the system's packet handling mechanisms. The issue is particularly concerning as it operates at the data plane level, meaning it affects the actual traffic processing capabilities rather than administrative functions.
The technical exploitation of this vulnerability occurs when specially crafted malformed TCP packets are transmitted to designated network endpoints within the F5 BIG-IP configuration. These packets contain malformed structures that cause the system to fail during packet parsing or processing operations, leading to service interruption. The control plane remains unaffected, indicating that the vulnerability specifically targets the data plane's packet forwarding and processing capabilities. This distinction is crucial for security teams as it limits the attack surface but still represents a significant operational risk. The vulnerability aligns with CWE-129, which describes issues related to insufficient validation of length of input buffers, and CWE-125, addressing out-of-bounds read conditions that can occur when processing malformed data.
The operational impact of CVE-2018-5517 extends beyond simple service disruption, potentially affecting business continuity and network availability for organizations relying on F5 BIG-IP load balancing and application delivery services. When service interruption occurs, it can affect thousands of concurrent connections and application endpoints, depending on the specific configuration and traffic volume. The vulnerability's presence in multiple patch levels within the 13.1.0 release series indicates a persistent flaw that required multiple remediation efforts. Organizations utilizing FastL4 virtual servers face particular risk as these components handle high-volume, low-latency traffic processing that is critical for application performance. The issue also impacts self IP addresses, which are essential for network routing and address resolution within F5 configurations.
Mitigation strategies for CVE-2018-5517 should prioritize immediate patching of affected F5 BIG-IP systems to version 13.1.0.6 or later, which contains the necessary code fixes. Network administrators should also implement packet filtering rules at network boundaries to identify and block malformed TCP traffic patterns that could exploit this vulnerability. The implementation of intrusion detection systems with signature-based detection capabilities can provide additional monitoring and alerting for potential exploitation attempts. Organizations should conduct thorough testing of patches in non-production environments before deployment to ensure compatibility with existing configurations. Security teams should also review their monitoring and alerting configurations to detect unusual traffic patterns that might indicate attempted exploitation. This vulnerability demonstrates the importance of maintaining up-to-date security patches and implementing defense-in-depth strategies that include both perimeter security controls and internal monitoring capabilities. The issue also highlights the need for organizations to maintain detailed inventories of their F5 BIG-IP deployments and their specific version configurations to quickly identify and remediate affected systems.