CVE-2019-6639 in BIG-IP AFM
Summary
by MITRE
On BIG-IP (AFM, PEM) 14.1.0-14.1.0.5, 14.0.0-14.0.0.4, 13.0.0-13.1.1.4, 12.1.0-12.1.4, 11.6.1-11.6.3.4, and 11.5.1-11.5.8, an undisclosed TMUI pages for AFM and PEM Subscriber management are vulnerable to a stored cross-site scripting (XSS) issue. This is a control plane issue only and is not accessible from the data plane. The attack requires a malicious resource administrator to store the XSS.
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Analysis
by VulDB Data Team • 10/17/2023
The vulnerability identified as CVE-2019-6639 represents a critical stored cross-site scripting flaw within the Traffic Management User Interface (TMUI) of F5 BIG-IP appliances, specifically affecting the Application Firewall Manager (AFM) and Policy Enforcement Manager (PEM) modules. This issue resides in the control plane of the system, meaning it operates at the management interface level rather than the data processing plane, which limits its direct impact on network traffic but maintains significant security implications for system administrators. The vulnerability affects multiple version ranges including 14.1.0 through 14.1.0.5, 14.0.0 through 14.0.0.4, 13.0.0 through 13.1.1.4, 12.1.0 through 12.1.4, 11.6.1 through 11.6.3.4, and 11.5.1 through 11.5.8, indicating a widespread exposure across several major releases of the F5 BIG-IP platform.
The technical flaw manifests as a stored XSS vulnerability within the TMUI pages responsible for AFM and PEM subscriber management functionality. This means that when a malicious actor with administrative privileges creates or modifies resources within these management interfaces, they can inject malicious JavaScript code that persists within the system. The vulnerability requires an authenticated attacker with administrative rights to execute the attack, as the XSS payload must be stored in the system's management interface rather than being triggered through external network requests. The control plane nature of this vulnerability means that attackers cannot exploit it through network-based attacks, but instead require access to the administrative management interface itself, making it particularly concerning for environments where administrative credentials might be compromised or where insider threats exist.
The operational impact of CVE-2019-6639 extends beyond simple XSS execution, as it allows a malicious administrator to potentially gain unauthorized access to sensitive system information, manipulate management interfaces, and potentially escalate privileges within the BIG-IP environment. The stored nature of the vulnerability means that the malicious code can affect any user who accesses the compromised management pages, creating a persistent threat vector that remains active until the malicious content is removed from the system. This vulnerability directly maps to CWE-79 which defines cross-site scripting flaws, and can be categorized under the ATT&CK framework as T1078 (Valid Accounts) and T1566 (Phishing) when considering how an attacker might gain administrative access to exploit this vulnerability. The control plane restriction means that while the attack surface is limited compared to data plane vulnerabilities, the potential for system compromise remains significant since management interfaces typically contain sensitive configuration data and administrative controls.
Mitigation strategies for CVE-2019-6639 primarily focus on implementing strict access controls and administrative privilege management to prevent unauthorized access to the BIG-IP management interfaces. Organizations should enforce the principle of least privilege for administrative accounts, implement multi-factor authentication for management access, and regularly audit administrative activities within the system. F5 released patches and updates to address this vulnerability, and organizations should immediately apply these security updates to affected systems. Network segmentation and monitoring of management interface access should be implemented to detect unauthorized access attempts, while regular security assessments of administrative interfaces should be conducted to identify potential compromise vectors. The vulnerability also underscores the importance of secure administrative practices, including regular credential rotation, secure password policies, and comprehensive security awareness training for system administrators to prevent insider threats and credential compromise scenarios.