CVE-2017-14190 in FortiOS
Summary
by MITRE
A Cross-site Scripting vulnerability in Fortinet FortiOS 5.6.0 to 5.6.2, 5.4.0 to 5.4.7, 5.2 and earlier, allows attacker to inject arbitrary web script or HTML via maliciously crafted "Host" header in user HTTP requests.
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Analysis
by VulDB Data Team • 02/02/2021
This cross-site scripting vulnerability exists within Fortinet FortiOS versions ranging from 5.6.0 through 5.6.2, 5.4.0 through 5.4.7, and all previous 5.2 releases. The flaw specifically resides in the handling of HTTP requests where the Host header parameter is not properly sanitized or validated before being processed by the web interface. This vulnerability falls under CWE-79 - Improper Neutralization of Input During Web Page Generation, which represents one of the most common and dangerous web application security flaws. The attack vector involves an attacker crafting malicious HTTP requests with specially designed Host headers that contain executable script code. When the FortiOS web interface processes these requests and displays the unfiltered Host header content, the embedded malicious code executes within the context of other users' browsers who access the affected system. This represents a classic server-side XSS vulnerability that can be exploited through the web administration interface or any HTTP service exposed by the FortiOS device. The impact extends beyond simple script execution as it can enable session hijacking, credential theft, and further escalation attacks against the network infrastructure. According to the ATT&CK framework, this vulnerability maps to T1059.007 - Command and Scripting Interpreter: JavaScript, as it leverages JavaScript execution within the browser context. The vulnerability affects the web management interface of FortiOS devices, making it particularly dangerous as administrators and users who access the system through web browsers become potential victims of the attack. The exploitation requires minimal privileges as it operates at the web application level and can be executed from any network location where the HTTP service is accessible, typically through the standard web management ports.
The technical implementation of this vulnerability stems from inadequate input validation within the HTTP request processing pipeline of FortiOS. When a user submits an HTTP request containing a malicious Host header, the system fails to properly encode or escape the header content before displaying it in the web interface. This allows attackers to inject HTML tags, JavaScript code, or other malicious payloads that execute in the browser context of legitimate users. The vulnerability is particularly concerning because the Host header is a standard part of HTTP requests and is often used for various purposes including virtual hosting and application routing. Attackers can leverage this by crafting requests that contain script tags or other malicious content within the Host header field. The web interface of FortiOS displays this information in various contexts including log entries, status pages, or administrative interfaces, where the unescaped content is rendered directly to the user's browser. The vulnerability demonstrates poor security practices in input sanitization and output encoding, which are fundamental requirements for preventing XSS attacks according to OWASP top ten security principles. The attack surface includes not only direct access to the management interface but also any web services that might be exposed by the FortiOS device, potentially affecting users who interact with the system through web-based applications or services.
The operational impact of this vulnerability extends significantly beyond simple script injection, creating potential pathways for advanced persistent threats and network compromise. An attacker who successfully exploits this vulnerability can steal administrative sessions, modify configuration settings, access sensitive logs, and potentially escalate privileges within the FortiOS environment. The attack can be particularly devastating when combined with other techniques such as session hijacking or credential theft, as the attacker gains access to the administrative interface of the firewall or security device. This creates a critical security risk for organizations that rely on FortiOS for network security, as compromising the management interface provides attackers with extensive control over network traffic filtering, access policies, and security configurations. The vulnerability also enables data exfiltration capabilities, allowing attackers to extract sensitive information from the device or network. According to ATT&CK framework, this vulnerability can be leveraged for T1566 - Phishing and T1567 - Exfiltration Over Web Service, as it can be used to redirect users to malicious sites or extract data through compromised web interfaces. Organizations using affected FortiOS versions face significant risk of unauthorized access to their network security infrastructure, potentially leading to complete network compromise. The vulnerability affects not only the immediate administrative interface but also any web-based services that may be exposed by the FortiOS device, making it a critical concern for network security teams.
Organizations should immediately implement mitigation strategies to address this vulnerability, starting with applying the latest Fortinet security patches and updates released to address this specific flaw. The vendor has issued firmware updates that properly sanitize the Host header content before display, preventing the execution of malicious scripts in the web interface. Network segmentation and access controls should be implemented to limit access to the FortiOS management interfaces, reducing the attack surface available to potential attackers. Regular monitoring of web logs and system events should be conducted to detect potential exploitation attempts, with particular attention to unusual Host header values or patterns. Input validation should be strengthened across all web applications and services to ensure that headers and parameters are properly sanitized before processing or display. The implementation of Content Security Policy headers can provide additional protection against script execution in the browser context, although this should not be considered a replacement for proper input sanitization. Security teams should also consider implementing web application firewalls to detect and block malicious Host header content. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in other network devices and applications. Training for administrators on recognizing and responding to potential XSS attacks is essential, as the vulnerability can be exploited through social engineering or automated scanning tools. The vulnerability serves as a reminder of the importance of proper input validation and output encoding in web applications, which are fundamental security practices recommended by both OWASP and NIST cybersecurity guidelines. Organizations should also implement network monitoring solutions that can detect unusual traffic patterns or malicious header content that may indicate exploitation attempts.