CVE-2020-7799 in FusionAuth
Summary
by MITRE
An issue was discovered in FusionAuth before 1.11.0. An authenticated user, allowed to edit e-mail templates (Home -> Settings -> Email Templates) or themes (Home -> Settings -> Themes), can execute commands on the underlying operating system by abusing freemarker.template.utility.Execute in the Apache FreeMarker engine that processes custom templates.
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Analysis
by VulDB Data Team • 03/27/2024
The vulnerability identified as CVE-2020-7799 represents a critical remote code execution flaw within FusionAuth authentication platform prior to version 1.11.0. This security issue stems from insufficient input validation and improper sanitization of user-supplied template content within the email template and theme editing functionalities. The vulnerability specifically affects authenticated users who possess permissions to modify email templates or themes through the FusionAuth administrative interface, creating a privilege escalation path that can be exploited to gain full system control.
The technical exploitation of this vulnerability relies on the Apache FreeMarker templating engine's built-in Execute utility, which is designed to execute system commands. When FusionAuth processes custom email templates or themes, it passes user-generated content through the FreeMarker engine without adequate sanitization measures. This allows authenticated attackers with template editing privileges to inject malicious FreeMarker directives that leverage the execute utility, effectively bypassing normal security boundaries and executing arbitrary commands with the privileges of the FusionAuth process. The vulnerability maps directly to CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and specifically aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: Python" and T1059.001 for "Command and Scripting Interpreter: PowerShell," as the underlying mechanism enables arbitrary command execution.
The operational impact of this vulnerability is severe and far-reaching, as it provides attackers with complete system compromise capabilities once they gain access to the FusionAuth administrative interface. An attacker could execute commands to escalate privileges, access sensitive data, install backdoors, or pivot to other systems within the network infrastructure. The vulnerability affects organizations that rely on FusionAuth for identity management, potentially exposing user credentials, authentication tokens, and sensitive organizational data. The exploitation requires only authenticated access with template editing permissions, making it particularly dangerous in environments where administrative privileges are not properly segmented or where users may have unnecessary access rights.
Organizations should immediately upgrade to FusionAuth version 1.11.0 or later to remediate this vulnerability. Additionally, implementing strict access controls and principle of least privilege should be enforced to limit who can edit email templates or themes within the system. Network segmentation and monitoring should be enhanced to detect unusual command execution patterns. Security teams should also consider implementing web application firewalls and input validation mechanisms to prevent malicious template content from being processed. The vulnerability demonstrates the critical importance of proper template sanitization and input validation in web applications, particularly when leveraging templating engines that have built-in system execution capabilities. Organizations should conduct comprehensive security assessments to identify and remediate similar vulnerabilities in other components of their authentication infrastructure, as this represents a significant vector for lateral movement and persistent access within enterprise environments.