CVE-2020-28246 in Form.io
Summary
by MITRE • 06/02/2022
A Server-Side Template Injection (SSTI) was discovered in Form.io 2.0.0. This leads to Remote Code Execution during deletion of the default Email template URL. NOTE: the email templating service was removed after 2020. Additionally, the vendor disputes this issue indicating this is sandboxed and only executable by admins.
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Analysis
by VulDB Data Team • 08/04/2024
The vulnerability identified as CVE-2020-28246 represents a critical server-side template injection flaw discovered in Form.io version 2.0.0 that exposes users to remote code execution risks. This vulnerability specifically manifests during the deletion process of the default email template URL, creating a dangerous attack vector that could allow malicious actors to execute arbitrary code on the affected server. The issue falls under the category of server-side template injection as defined by CWE-74, which occurs when user-supplied data is directly inserted into template code without proper sanitization or validation. The vulnerability's exploitation pathway demonstrates how seemingly benign administrative operations can become dangerous when template processing lacks adequate input validation mechanisms.
The operational impact of this vulnerability extends beyond simple code execution to encompass potential complete system compromise, as the injection occurs within the email templating service context. The fact that this service was removed after 2020 does not diminish the significance of the vulnerability, as many organizations may still be operating legacy systems that have not been updated to newer versions. Attackers could leverage this vulnerability to escalate privileges, access sensitive data, or establish persistent backdoors within the affected infrastructure. The vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter, and T1078.004 for valid accounts, as exploitation would likely require administrative access to leverage the sandboxed execution environment effectively.
Security researchers have noted that while the vendor initially disputes the severity of this issue by claiming the functionality is sandboxed and restricted to administrator access, this defense mechanism proves insufficient in real-world scenarios. The sandboxing approach commonly fails when the underlying template engine allows for path traversal or when administrative credentials are compromised through other attack vectors. The vulnerability demonstrates how even restricted execution environments can be bypassed through creative exploitation techniques that manipulate the template processing pipeline. Organizations implementing Form.io or similar form management platforms should consider this vulnerability as a critical risk requiring immediate remediation, regardless of the vendor's stance on its severity.
Mitigation strategies should focus on immediate patching of affected systems and implementation of comprehensive input validation measures for all template processing operations. Organizations should also implement network segmentation to limit access to administrative functions and deploy web application firewalls to detect and block suspicious template injection attempts. The remediation approach should include disabling unused template services and implementing strict access controls for administrative functions. Additionally, security monitoring should be enhanced to detect anomalous behavior patterns associated with template processing activities, as these can serve as early indicators of exploitation attempts. Regular security assessments of template processing components should be conducted to identify similar vulnerabilities in other parts of the application stack, as template injection flaws often occur in related components within the same software ecosystem.