CVE-2018-5537 in BIG-IP
Summary
by MITRE
A remote attacker may be able to disrupt services on F5 BIG-IP 13.0.0-13.1.0.5, 12.1.0-12.1.3.5, 11.6.0-11.6.3.1, or 11.2.1-11.5.6 if the TMM virtual server is configured with a HTML or a Rewrite profile. TMM may restart while processing some specially prepared HTML content from the back end.
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Analysis
by VulDB Data Team • 04/25/2023
The vulnerability described in CVE-2018-5537 represents a significant service disruption risk within F5 BIG-IP load balancing appliances, specifically affecting versions ranging from 11.2.1 through 13.1.0.5. This issue manifests when the Traffic Management Microkernel (TMM) virtual server operates with HTML or Rewrite profiles, creating a condition where maliciously crafted backend HTML content can trigger unexpected system restarts. The vulnerability falls under the category of denial of service attacks that exploit application layer processing flaws, potentially allowing remote attackers to compromise service availability without requiring authentication or privileged access.
The technical flaw resides in how the TMM processes HTML content when specific profiles are enabled, particularly when handling specially crafted HTML elements or sequences that cause memory corruption or processing errors within the traffic management kernel. This type of vulnerability demonstrates characteristics consistent with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflows, though the exact mechanism likely involves improper input validation or memory handling during HTML parsing operations. The vulnerability exploits the interaction between the application layer processing and the underlying kernel components, creating a scenario where malformed input can cause the system to crash or restart.
The operational impact of this vulnerability extends beyond simple service disruption, as it can affect critical infrastructure components that rely on F5 BIG-IP appliances for load balancing and traffic management. Organizations using affected versions may experience unexpected downtime, service degradation, or potential data loss during the restart process, especially in high-availability environments where seamless operation is crucial. The vulnerability's remote exploitability means that attackers can potentially trigger these disruptions from outside the network perimeter, making it particularly dangerous for publicly accessible services. According to ATT&CK framework, this vulnerability maps to T1499.004 (Endpoint Denial of Service) and T1595.001 (Network Denial of Service) techniques, representing both endpoint and network-level service disruption capabilities.
Mitigation strategies for CVE-2018-5537 should prioritize immediate patching of affected F5 BIG-IP appliances to the latest available versions that contain the necessary security fixes. Organizations should also implement network segmentation and access controls to limit exposure of affected systems, while monitoring for unusual traffic patterns or service restarts that might indicate exploitation attempts. Additional defensive measures include disabling HTML or Rewrite profiles on virtual servers when not strictly necessary, implementing web application firewalls to filter malicious content, and establishing robust incident response procedures to quickly address any exploitation attempts. The vulnerability highlights the importance of regular security updates and proper configuration management in maintaining network infrastructure security.