CVE-2019-19902 in Backdrop
Summary
by MITRE
An issue was discovered in Backdrop CMS 1.13.x before 1.13.5 and 1.14.x before 1.14.2. It allows the upload of entire-site configuration archives through the user interface or command line. It does not sufficiently check uploaded archives for invalid data, allowing non-configuration scripts to potentially be uploaded to the server. This issue is mitigated by the fact that the attacker would be required to have the "Synchronize, import, and export configuration" permission, a permission that only trusted administrators should be given. Other measures in the product prevent the execution of PHP scripts, so another server-side scripting language must be accessible on the server to execute code.
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Analysis
by VulDB Data Team • 03/16/2024
The vulnerability identified as CVE-2019-19902 affects Backdrop CMS versions prior to 1.13.5 and 1.14.2, representing a critical configuration management flaw that could potentially enable arbitrary code execution. This issue stems from insufficient validation mechanisms within the CMS's configuration import functionality, specifically when processing archive files through the user interface or command line interfaces. The flaw allows attackers to upload complete site configuration archives that may contain malicious scripts alongside legitimate configuration data, creating a vector for privilege escalation and server compromise.
The technical nature of this vulnerability aligns with CWE-434, which addresses the improper restriction of file uploads, and represents a classic case of inadequate input validation and sanitization. The system fails to properly inspect uploaded archive contents for potentially harmful files, particularly non-configuration scripts that could execute on the server. While the vulnerability requires specific permissions to exploit, the attacker must possess the "Synchronize, import, and export configuration" privilege, which should only be granted to trusted administrators. This permission model provides a baseline defense mechanism, but the underlying flaw in archive validation creates an exploitable gap in the security posture.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it could enable attackers to execute arbitrary code on the server, potentially leading to complete system compromise. The attack vector becomes particularly dangerous when considering that the system's defenses against PHP script execution are circumvented, requiring only that another server-side scripting language be available on the server to achieve code execution. This scenario creates a multi-layered threat model where even if PHP execution is blocked, other scripting languages such as Python, Perl, or shell scripts could be leveraged for malicious purposes. The vulnerability essentially transforms a configuration management interface into a potential code execution channel, particularly concerning for environments where multiple scripting languages are present.
Security mitigations for this vulnerability primarily focus on immediate patching of affected Backdrop CMS versions to the recommended secure releases. Organizations should implement strict access controls and ensure that only trusted administrators possess the configuration synchronization permissions. Additionally, server-level restrictions should be implemented to prevent execution of non-configuration scripts, including the use of file type whitelisting, proper file permissions, and content validation. The principle of least privilege should be strictly enforced, and regular security audits should verify that configuration import functions are properly secured. This vulnerability highlights the importance of input validation and the necessity of implementing comprehensive file upload restrictions, particularly for administrative interfaces that handle sensitive system configuration data. The issue demonstrates how seemingly benign functionality can become a critical security risk when proper validation and sanitization mechanisms are absent from the system architecture.