CVE-2019-6600 in BIG-IP
Summary
by MITRE
In BIG-IP 14.0.0-14.0.0.2, 13.0.0-13.1.1.3, 12.1.0-12.1.3.7, 11.6.1-11.6.3.2, or 11.5.1-11.5.8, when remote authentication is enabled for administrative users and all external users are granted the "guest" role, unsanitized values can be reflected to the client via the login page. This can lead to a cross-site scripting attack against unauthenticated clients.
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Analysis
by VulDB Data Team • 08/01/2023
The vulnerability described in CVE-2019-6600 affects F5 BIG-IP appliances across multiple version ranges, specifically targeting the authentication and session management components. This issue arises when administrators configure remote authentication for administrative users while granting all external users the "guest" role, creating a dangerous configuration that exposes the system to cross-site scripting attacks. The flaw represents a critical security oversight in how the system handles user input validation and output encoding during the authentication process. The vulnerability manifests through the login page where unsanitized user-supplied values are directly reflected back to clients without proper input sanitization or output encoding mechanisms.
The technical exploitation of this vulnerability occurs through a classic cross-site scripting attack vector where malicious actors can inject malicious scripts into the login page through improperly validated user inputs. When the system reflects these unsanitized values back to the browser, any script content gets executed in the context of the victim's session, potentially allowing attackers to steal session cookies, redirect users to malicious sites, or perform actions on behalf of authenticated users. This vulnerability falls under CWE-79 which specifically addresses cross-site scripting flaws in web applications. The attack chain begins with an attacker crafting malicious input that gets processed by the system's authentication module and subsequently reflected back to the browser without proper sanitization, making it a server-side vulnerability that can be exploited by unauthenticated attackers.
The operational impact of CVE-2019-6600 extends beyond simple XSS exploitation, as it can compromise the entire administrative session management framework of the BIG-IP appliance. Attackers who successfully exploit this vulnerability can potentially escalate privileges, gain unauthorized access to sensitive administrative functions, or establish persistent access points within the network infrastructure. The vulnerability affects organizations that rely on BIG-IP for load balancing, application delivery, and security services, making it particularly dangerous for enterprises with complex network architectures. This weakness creates a potential entry point for attackers to move laterally within networks, as the compromised appliance could serve as a foothold for broader attacks. The vulnerability's impact is amplified by the fact that it affects multiple major version lines of the BIG-IP platform, indicating a widespread exposure across different deployment scenarios.
Organizations should implement immediate mitigations including disabling remote authentication for administrative users when guest roles are enabled, implementing comprehensive input validation and output encoding mechanisms, and applying the latest security patches provided by F5. The recommended approach involves configuring proper access controls to prevent guest users from accessing administrative functions while maintaining secure authentication mechanisms. Security teams should also deploy web application firewalls and implement content security policies to prevent script execution in the browser context. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access through web application exploitation and privilege escalation. Organizations should conduct comprehensive security assessments to identify affected systems and ensure proper configuration management to prevent unauthorized access to administrative interfaces. The vulnerability underscores the importance of proper input validation and output encoding practices in web applications, as outlined in industry standards and security frameworks.