CVE-2020-15937 in FortiGate
Summary
by MITRE • 03/04/2021
An improper neutralization of input vulnerability in FortiGate version 6.2.x below 6.2.5 and 6.4.x below 6.4.1 may allow a remote attacker to perform a stored cross site scripting attack (XSS) via the IPS and WAF logs dashboard.
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Analysis
by VulDB Data Team • 03/14/2021
This vulnerability represents a critical security flaw in Fortinet FortiGate appliances affecting versions 6.2.x below 6.2.5 and 6.4.x below 6.4.1. The issue stems from inadequate input validation and sanitization within the IPS and WAF logs dashboard functionality, creating an environment where malicious actors can inject persistent malicious scripts. The vulnerability falls under CWE-79 which specifically addresses Cross-Site Scripting flaws, making it a prime target for attackers seeking to exploit web application security weaknesses. The stored nature of this XSS vulnerability means that malicious scripts are permanently stored on the server and executed whenever legitimate users access the affected dashboard, creating a persistent threat vector that can compromise user sessions and exfiltrate sensitive data.
The technical implementation of this flaw occurs within the FortiGate's web interface processing of log data, particularly when displaying IPS and WAF events. When administrators or users view the logs dashboard, the application fails to properly sanitize user-supplied input that may have been included in the log entries themselves. This allows attackers who can influence log content through various means such as crafting malicious network traffic or exploiting other vulnerabilities to inject malicious JavaScript code that gets executed in the context of other users' browsers. The vulnerability is particularly concerning because it operates within the administrative interface where privileged users typically access sensitive security information, potentially allowing attackers to escalate their privileges or gain unauthorized access to critical network security functions.
The operational impact of this vulnerability extends beyond simple script execution, as it can be leveraged to perform session hijacking, credential theft, and data exfiltration attacks. Attackers could potentially redirect users to malicious domains, inject malicious content into security dashboards, or even use the compromised interface to manipulate security policies. The attack surface is particularly dangerous in enterprise environments where FortiGate appliances serve as central security gateways, as successful exploitation could provide attackers with access to critical network monitoring data and potentially allow them to bypass other security controls. This vulnerability aligns with ATT&CK technique T1566.001 which covers the use of malicious content in web applications, and T1071.004 which involves application layer protocol manipulation.
Organizations should immediately implement mitigations including updating to Fortinet FortiOS versions 6.2.5 or 6.4.1 and later, which contain the necessary patches to address this vulnerability. Network segmentation and monitoring of administrative interfaces should be enhanced to detect potential exploitation attempts. Additionally, implementing Content Security Policy headers and regular security audits of web applications can help reduce the risk of successful exploitation. The vulnerability demonstrates the critical importance of input validation in web applications and highlights the need for comprehensive security testing of administrative interfaces that handle user-supplied data. Organizations should also consider implementing web application firewalls and regular penetration testing to identify similar vulnerabilities in their security infrastructure.