CVE-2018-5511 in BIG-IP
Summary
by MITRE
On F5 BIG-IP 13.1.0-13.1.0.3 or 13.0.0, when authenticated administrative users execute commands in the Traffic Management User Interface (TMUI), also referred to as the BIG-IP Configuration utility, restrictions on allowed commands may not be enforced.
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Analysis
by VulDB Data Team • 10/19/2025
The vulnerability identified as CVE-2018-5511 represents a critical authorization bypass flaw within F5 BIG-IP systems that affects versions 13.1.0 through 13.1.0.3 and 13.0.0. This issue resides in the Traffic Management User Interface component, commonly known as the BIG-IP Configuration utility, which serves as the primary administrative interface for managing F5 load balancers and application delivery controllers. The vulnerability stems from insufficient input validation and command restriction enforcement mechanisms within the TMUI subsystem, creating a pathway for authenticated administrative users to bypass intended security controls and execute unauthorized commands. This flaw fundamentally undermines the principle of least privilege that should govern administrative access to critical network infrastructure components.
The technical exploitation of CVE-2018-5511 occurs when authenticated administrative users interact with the TMUI interface and manipulate command execution parameters in ways that circumvent built-in security controls. The vulnerability manifests through improper sanitization of user inputs passed to backend command processing functions, allowing attackers to inject arbitrary commands that would normally be restricted. This issue falls under the CWE-79 category of Cross-Site Scripting, though it specifically impacts command execution rather than script injection, and aligns with CWE-284 for improper access control. The flaw essentially creates a command injection vulnerability within the administrative interface, where the system fails to properly validate or filter user-supplied command parameters before processing them through the underlying operating system shell or command execution engine.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it enables authenticated administrators to execute arbitrary code on the BIG-IP system with the highest possible privileges. Attackers who can authenticate to the administrative interface can leverage this flaw to gain complete control over the device, potentially leading to data exfiltration, service disruption, or use as a pivot point for attacking internal network resources. The vulnerability affects the core configuration management capabilities of F5 devices, which are typically considered highly privileged interfaces with direct access to network traffic control and security policy enforcement mechanisms. This creates a significant risk for organizations relying on F5 BIG-IP systems for application delivery and security services, as compromise of these devices can result in complete network exposure and loss of critical security controls.
Organizations should implement immediate mitigations including applying the official F5 security patches released in response to this vulnerability, which address the underlying command validation and enforcement mechanisms. Network segmentation and additional access controls should be implemented to limit administrative access to only trusted personnel and systems. The vulnerability demonstrates the critical importance of maintaining up-to-date security patches and implementing defense-in-depth strategies for critical infrastructure components. Security monitoring should be enhanced to detect anomalous command execution patterns within administrative interfaces, and privileged access should be closely audited using principles aligned with the NIST Cybersecurity Framework and ISO 27001 standards. Additionally, organizations should consider implementing multi-factor authentication for administrative access and regular security assessments to identify similar authorization bypass vulnerabilities in other network infrastructure components.