CVE-2017-7734 in FortiOS
Summary
by MITRE
A Cross-Site Scripting vulnerability in Fortinet FortiOS versions 5.4.0 through 5.4.4 allows attackers to execute unauthorized code or commands via Comments while saving Config Revisions.
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Analysis
by VulDB Data Team • 12/28/2020
The vulnerability identified as CVE-2017-7734 represents a critical cross-site scripting flaw within Fortinet FortiOS operating systems version 5.4.0 through 5.4.4. This weakness specifically manifests when users interact with the configuration revision management system, particularly during the process of saving configuration changes with associated comments. The vulnerability stems from inadequate input validation and output encoding mechanisms within the web interface of the FortiOS system, creating a pathway for malicious actors to inject malicious scripts into the configuration management workflow.
The technical implementation of this vulnerability resides in the improper sanitization of user-supplied data within the comments field of configuration revisions. When administrators or users save configuration changes with descriptive comments, the system fails to adequately filter or encode special characters that could be interpreted as executable script code. This processing gap allows attackers to embed malicious javascript code within the comment fields, which then gets executed when other users view the configuration revision history or related administrative interfaces. The vulnerability operates at the application layer and specifically targets the web-based management interface of FortiOS, making it particularly dangerous for network administrators who regularly interact with the system's configuration management features.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with a potential foothold for more sophisticated attacks within the network infrastructure. An attacker who successfully exploits this vulnerability can execute unauthorized commands on the affected FortiOS device, potentially gaining administrative privileges or manipulating network security policies. The attack vector is particularly concerning because it leverages legitimate administrative functionality, making it harder to detect and distinguish from normal user behavior. This vulnerability affects organizations that rely on Fortinet firewalls for network security, potentially compromising the integrity of their security configurations and exposing critical network assets to unauthorized access.
Organizations affected by this vulnerability should prioritize immediate remediation through official Fortinet security patches and updates. The recommended mitigation strategy involves upgrading to FortiOS version 5.4.5 or later, which includes proper input validation and output encoding mechanisms to prevent script injection attacks. Additionally, network administrators should implement monitoring solutions to detect unusual activity in configuration revision comments and consider implementing web application firewalls to filter malicious payloads. Security teams should also conduct thorough vulnerability assessments of their Fortinet deployments and review access controls to limit who can modify configuration revisions. This vulnerability aligns with CWE-79, which describes cross-site scripting flaws, and represents a significant concern for organizations following ATT&CK framework's TA0001 Initial Access and TA0003 Persistence tactics, as it enables attackers to establish unauthorized access and maintain control over network security devices. The vulnerability demonstrates the critical importance of input validation in web applications and highlights the need for comprehensive security testing of administrative interfaces in network infrastructure devices.