CVE-2017-7735 in FortiOS
Summary
by MITRE
A Cross-Site Scripting vulnerability in Fortinet FortiOS versions 5.2.0 through 5.2.11 and 5.4.0 through 5.4.4 allows attackers to execute unauthorized code or commands via the "Groups" input while creating or editing User Groups.
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Analysis
by VulDB Data Team • 12/28/2020
The vulnerability identified as CVE-2017-7735 represents a critical cross-site scripting flaw within Fortinet FortiOS software versions 5.2.0 through 5.2.11 and 5.4.0 through 5.4.4. This weakness resides in the web-based management interface of the FortiOS operating system, specifically affecting the user group creation and editing functionality. The vulnerability stems from inadequate input validation and sanitization mechanisms within the Groups parameter handling process, creating an exploitable vector for malicious actors to inject arbitrary script code into the web application's response. The flaw operates by allowing unvalidated user input to be directly rendered in the web interface without proper encoding or escaping, enabling attackers to manipulate the application's behavior through crafted payload delivery.
The technical implementation of this vulnerability falls under CWE-79 - Improper Neutralization of Input During Web Page Generation, which is a fundamental web application security weakness that enables attackers to inject malicious scripts into web pages viewed by other users. The attack surface is particularly concerning as it targets administrative functions within the FortiOS environment, where user groups represent critical access control mechanisms. When an attacker successfully exploits this vulnerability, they can execute unauthorized commands or code within the context of the victim user's browser session, potentially leading to privilege escalation and complete system compromise. The vulnerability's impact extends beyond simple script execution as it can be leveraged to perform session hijacking, data exfiltration, and unauthorized administrative actions through the compromised user group management interface.
The operational implications of CVE-2017-7735 are severe for organizations relying on Fortinet firewalls and security appliances, as user group management represents a core administrative function for access control and network security policy enforcement. Attackers can exploit this vulnerability to manipulate user permissions, create backdoor accounts, or escalate privileges within the network security infrastructure. The attack vector is particularly dangerous because it requires minimal user interaction beyond accessing the vulnerable management interface, making it susceptible to both targeted attacks and automated exploitation. This vulnerability directly impacts the integrity and confidentiality of the security infrastructure, potentially allowing attackers to bypass security controls and gain unauthorized access to protected network resources. The exploitability of this vulnerability aligns with ATT&CK technique T1059.007 - Command and Scripting Interpreter: PowerShell, as attackers can leverage the XSS payload to execute malicious commands through the compromised web interface.
Organizations must implement immediate mitigations including applying the latest Fortinet security patches and firmware updates that address this specific vulnerability. Network administrators should also consider implementing additional security controls such as web application firewalls, input validation rules, and monitoring for suspicious user group creation or modification activities. The vulnerability highlights the importance of proper input sanitization and output encoding practices in web applications, particularly those handling administrative functions. Security teams should conduct comprehensive vulnerability assessments of their Fortinet infrastructure and review user group management policies to ensure that access controls remain intact. Additionally, implementing multi-factor authentication and role-based access controls can provide defense-in-depth measures that limit the potential impact of such vulnerabilities. The remediation process should include thorough testing of patched systems to ensure that the XSS vulnerability is completely eliminated while maintaining all necessary administrative functionality.