CVE-2020-7685 in UmbracoForms
Summary
by MITRE
This affects all versions of package UmbracoForms. When using the default configuration for upload forms, it is possible to upload arbitrary file types.
 
 The package offers a way for users to mitigate the issue. The users of this package can create a custom workflow and frontend validation that blocks certain file types, depending on their security needs and policies.
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Analysis
by VulDB Data Team • 11/06/2020
The vulnerability identified as CVE-2020-7685 impacts all versions of the UmbracoForms package, a widely used form building solution within the Umbraco content management system ecosystem. This security flaw represents a critical misconfiguration that fundamentally undermines the platform's file upload security controls, creating an environment where malicious actors can bypass intended restrictions and upload potentially harmful files to target systems. The issue specifically manifests when utilizing the default configuration settings for upload forms, which fail to implement proper file type validation mechanisms. This vulnerability falls under the category of insecure file handling practices and aligns with CWE-434, which addresses the improper restriction of uploads of executable files.
The technical implementation of this vulnerability stems from the package's default behavior of accepting all file types without adequate filtering or validation processes. When users configure forms for file uploads, the system does not enforce a whitelist approach or implement proper MIME type checking, allowing attackers to submit files with extensions such as .exe, .bat, .jsp, or other potentially malicious formats. This flaw creates a pathway for arbitrary code execution, data exfiltration, and system compromise through malicious file uploads. The vulnerability's impact is amplified by the fact that it affects all versions of the package, indicating a fundamental architectural weakness rather than a specific code flaw that could be patched. The security implications extend beyond simple file uploads to encompass potential remote code execution, privilege escalation, and persistent threat vectors within the target environment.
The operational impact of CVE-2020-7685 is severe and multifaceted, particularly for organizations relying on UmbracoForms for content management and user interaction. Attackers can leverage this vulnerability to upload malicious payloads such as web shells, malware, or phishing materials, potentially leading to complete system compromise. The default configuration nature of this vulnerability means that organizations may unknowingly expose themselves to risk without implementing additional security measures. This flaw directly relates to ATT&CK technique T1190, which involves exploiting vulnerabilities in web applications to gain initial access or escalate privileges. The vulnerability also aligns with ATT&CK technique T1078, representing a potential path for adversaries to establish persistent access through malicious file uploads. Organizations using UmbracoForms without proper mitigation measures face significant risk of data breaches, service disruption, and compliance violations.
The recommended mitigation strategies for this vulnerability involve implementing custom security controls as suggested in the original advisory. Organizations should develop custom workflows that enforce strict file type validation and implement comprehensive frontend validation mechanisms to block unauthorized file extensions. These custom solutions should establish a whitelist approach for acceptable file types and integrate robust MIME type checking to prevent bypass attempts. Additionally, organizations should consider implementing server-side validation controls that complement frontend measures, ensuring that even if client-side validation is bypassed, the server will still reject malicious file uploads. The mitigation approach should align with security best practices outlined in NIST SP 800-53 and ISO/IEC 27001 standards, emphasizing the principle of least privilege and defense in depth. Regular security assessments and monitoring of file upload activities should be implemented to detect and respond to potential exploitation attempts. Organizations must also update their security policies to address the specific risks associated with file upload functionality and ensure that all stakeholders understand the importance of proper configuration management.