CVE-2016-9257 in BIG-IP
Summary
by MITRE
In F5 BIG-IP APM 12.0.0 through 12.1.2, non-authenticated users may be able to inject JavaScript into a request that will then be rendered and executed in the context of the Administrative user when the Administrative user is viewing the Access System Logs, allowing the non-authenticated user to carry out a Cross Site Scripting (XSS) attack against the Administrative user.
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Analysis
by VulDB Data Team • 12/06/2022
The vulnerability identified as CVE-2016-9257 represents a critical cross site scripting flaw within the F5 BIG-IP Access Policy Manager component. This vulnerability exists in versions 12.0.0 through 12.1.2 of the F5 BIG-IP APM software, creating a persistent security weakness that allows unauthenticated attackers to inject malicious JavaScript code into system requests. The flaw specifically manifests when administrative users view access system logs, providing attackers with a sophisticated vector for privilege escalation and system compromise.
The technical implementation of this vulnerability stems from inadequate input validation and output encoding within the logging and display mechanisms of the APM component. When non-authenticated users submit specially crafted requests containing malicious JavaScript payloads, these inputs are not properly sanitized before being stored in the system logs. Subsequently, when administrative users access these logs for monitoring or troubleshooting purposes, the stored JavaScript code executes within the administrative user's browser context, bypassing normal authentication and authorization controls. This represents a classic server-side cross site scripting vulnerability where the attack vector originates from user-supplied data that should never be trusted or directly rendered.
The operational impact of this vulnerability extends far beyond simple data theft or defacement. An attacker who successfully exploits this flaw can execute arbitrary JavaScript code in the administrative context, potentially allowing them to escalate privileges, access sensitive system information, modify configurations, or even take complete control of the BIG-IP appliance. The vulnerability is particularly dangerous because it requires no authentication to exploit, making it accessible to anyone who can reach the affected system. This creates a significant risk for organizations that have their BIG-IP systems exposed to untrusted networks, as the attack can be carried out by anyone with network access to the appliance's management interfaces.
From a cybersecurity framework perspective, this vulnerability aligns with CWE-79 - Cross-site Scripting and maps to ATT&CK technique T1059.007 - Command and Scripting Interpreter: JavaScript. The vulnerability demonstrates poor input sanitization practices and highlights the critical importance of implementing proper output encoding for all user-supplied data that may be rendered in web contexts. Organizations utilizing F5 BIG-IP systems should immediately implement mitigations including applying the vendor's security patches, implementing network segmentation to limit access to administrative interfaces, and deploying web application firewalls to detect and block malicious JavaScript payloads. Additionally, regular security assessments should verify that all user inputs are properly validated and sanitized before being processed or stored within system logs.
The exploitation of this vulnerability represents a sophisticated attack pattern that leverages the trust relationship between administrative users and system logs. Administrative users typically view logs with elevated privileges and assume the content is safe, creating an ideal environment for social engineering attacks. The vulnerability essentially transforms the administrative log viewing process into an attack surface, where the simple act of monitoring system activity becomes a potential point of compromise. Organizations should consider implementing additional monitoring for suspicious log entries and establish incident response procedures specifically addressing this type of attack vector to minimize potential damage from successful exploitation attempts.