CVE-2018-19907 in Crafter
Summary
by MITRE
A Server-Side Template Injection issue was discovered in Crafter CMS 3.0.18. Attackers with developer privileges may execute OS commands by Creating/Editing a template file (.ftl filetype) that triggers a call to freemarker.template.utility.Execute in the FreeMarker library during rendering of a web page.
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Analysis
by VulDB Data Team • 06/13/2023
The vulnerability CVE-2018-19907 represents a critical server-side template injection flaw in Crafter CMS version 3.0.18 that fundamentally undermines the application's security posture. This issue arises from the improper handling of template files within the content management system, specifically when processing .ftl files that utilize the FreeMarker templating engine. The vulnerability is particularly dangerous because it allows attackers with developer privileges to escalate their access and execute arbitrary operating system commands, effectively bypassing the application's intended security boundaries and potentially compromising the entire server infrastructure.
The technical root cause of this vulnerability stems from the insecure usage of the freemarker.template.utility.Execute function within the FreeMarker library. When Crafter CMS processes template files containing malicious code, the system fails to properly sanitize or validate user input before passing it to the FreeMarker engine's execution utility. This creates an injection point where attacker-controlled template content can be interpreted and executed as system commands. The vulnerability is classified under CWE-94, which specifically addresses "Improper Control of Generation of Code ('Code Injection')" and aligns with the ATT&CK technique T1059.001 for Command and Scripting Interpreter. The flaw manifests when the CMS renders web pages that contain templates with embedded FreeMarker directives that invoke the execute utility, creating a direct pathway for command execution.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it enables attackers to gain complete control over the affected server environment. Once exploited, an attacker can execute arbitrary commands with the privileges of the web application user, potentially leading to data exfiltration, system compromise, or further lateral movement within the network. The vulnerability is particularly concerning in enterprise environments where Crafter CMS is used for content management, as it provides a direct attack vector that can be leveraged to compromise sensitive corporate data. The attack requires only developer-level privileges, making it accessible to insiders or attackers who have gained access to such accounts, and the exploitation is relatively straightforward since it involves creating or editing template files that trigger the vulnerable FreeMarker functionality.
Organizations should implement immediate mitigations including restricting file upload and editing capabilities for template files, implementing strict input validation and sanitization for all user-supplied template content, and applying the latest security patches from Crafter CMS developers. The recommended approach involves configuring the FreeMarker engine to disable potentially dangerous utilities like Execute, implementing proper access controls to limit template editing privileges, and conducting thorough code reviews to identify any other instances of insecure template processing. Security teams should also monitor for unusual template modifications and implement network-level detection measures to identify potential exploitation attempts. Additionally, organizations should consider implementing principle of least privilege access controls for developer accounts and establish proper segregation of duties to minimize the risk of template-based command execution attacks. The vulnerability demonstrates the critical importance of secure template handling in web applications and serves as a reminder of the potential consequences when templating engines are improperly configured or when security controls are insufficiently implemented.