CVE-2019-6699 in FortiADC
Summary
by MITRE
An improper neutralization of input vulnerability in Fortinet FortiADC 5.3.3 and earlier may allow an attacker to execute a stored Cross Site Scripting (XSS) via a field in the traffic group interface.
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Analysis
by VulDB Data Team • 03/14/2020
The vulnerability identified as CVE-2019-6699 represents a critical security flaw in Fortinet FortiADC appliances running version 5.3.3 and earlier. This issue manifests as an improper neutralization of input data within the traffic group interface functionality, creating a pathway for malicious actors to inject persistent cross-site scripting payloads. The vulnerability specifically affects the handling of user-supplied input in traffic group configuration fields, where insufficient sanitization allows attackers to store malicious scripts that execute when other users interact with the affected interface.
The technical implementation of this vulnerability stems from inadequate input validation and sanitization mechanisms within the FortiADC management interface. When administrators or users configure traffic group parameters, the system fails to properly escape or filter special characters that could be interpreted as executable script code. This weakness aligns with CWE-79, which categorizes cross-site scripting vulnerabilities as improper neutralization of input data. The flaw exists at the application layer where user-controllable data enters the system without proper security controls to prevent malicious code execution.
Operational impact of this vulnerability extends beyond simple script injection, as it provides attackers with persistent access to the administrative interface. Once an attacker successfully stores malicious XSS payloads through the traffic group configuration, these scripts execute in the context of other authenticated users' browsers, potentially enabling session hijacking, credential theft, or further privilege escalation within the FortiADC environment. The stored nature of the vulnerability means that the malicious code persists even after the initial injection, making it particularly dangerous for long-term attacks and persistent threats. This vulnerability directly impacts the integrity and confidentiality of the FortiADC management interface, potentially compromising the entire load balancing and application delivery infrastructure.
Organizations should immediately implement mitigations including upgrading to Fortinet FortiADC versions 5.4.0 or later, which contain patches addressing this vulnerability. Network segmentation and access controls should be enhanced to limit administrative access to the FortiADC interface, while regular monitoring of traffic group configuration changes can help detect potential injection attempts. Security teams should also implement web application firewalls to detect and block suspicious input patterns, and conduct thorough penetration testing to identify any other potential injection points within the FortiADC management interface. The ATT&CK framework categorizes this vulnerability under T1059.007 for scripting and T1566.001 for malicious file execution, highlighting the persistent threat nature of stored XSS attacks that can be leveraged for broader system compromise.