CVE-2017-3127 in FortiOS
Summary
by MITRE
A Cross-Site Scripting vulnerability in Fortinet FortiGate 5.2.0 through 5.2.10 allows attacker to execute unauthorized code or commands via the srcintf parameter during Firewall Policy Creation.
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Analysis
by VulDB Data Team • 01/11/2020
The vulnerability identified as CVE-2017-3127 represents a critical cross-site scripting flaw discovered in Fortinet FortiGate firewall appliances running firmware versions 5.2.0 through 5.2.10. This security weakness specifically manifests during the firewall policy creation process when the system processes the srcintf parameter, which defines the source interface for network traffic. The flaw enables malicious actors to inject arbitrary script code into the web interface, potentially compromising the administrative console and gaining unauthorized access to network security controls. The vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is classified as a persistent threat that can lead to complete system compromise when exploited by attackers with minimal privileges.
The technical exploitation of this vulnerability occurs through manipulation of the srcintf parameter during firewall policy configuration, where insufficient input validation and output sanitization allow malicious payloads to be stored and subsequently executed when the affected web interface renders the policy information. Attackers can leverage this weakness to inject malicious JavaScript code that executes within the context of the administrator's browser session, potentially leading to session hijacking, privilege escalation, or unauthorized modification of firewall rules. The vulnerability's impact is particularly severe because it targets the administrative web interface of enterprise-grade firewalls, which are critical components of network security infrastructure and typically require elevated privileges to access and modify.
The operational implications of CVE-2017-3127 extend beyond simple script injection, as successful exploitation can result in complete compromise of the FortiGate appliance and potentially the entire network infrastructure it protects. An attacker who successfully exploits this vulnerability could gain persistent access to the firewall's administrative functions, modify security policies, redirect traffic, or establish backdoor access points within the network. This threat scenario aligns with ATT&CK technique T1071.004 for application layer protocol tunneling and T1566 for credential harvesting through social engineering, as the vulnerability enables attackers to manipulate the web interface to extract sensitive information or establish persistent access. Organizations using affected FortiGate models face significant risk of lateral movement within their network when this vulnerability is exploited, as the compromised firewall serves as a critical gateway for network traffic.
Organizations should immediately implement mitigation strategies including firmware updates to versions that address the XSS vulnerability, as Fortinet released patches specifically targeting this flaw in subsequent releases. Network segmentation and monitoring of administrative interfaces can help detect anomalous behavior associated with exploitation attempts, while implementing proper input validation and output encoding practices in web applications can prevent similar vulnerabilities from occurring in other systems. The vulnerability demonstrates the importance of maintaining current firmware versions and conducting regular security assessments of network infrastructure components, particularly those with web-based administrative interfaces. Security teams should also consider implementing web application firewalls and strict access controls for administrative interfaces to minimize the attack surface and reduce the likelihood of successful exploitation.