CVE-2020-9280 in SilverStripe
Summary
by MITRE
In SilverStripe through 4.5, files uploaded via Forms to folders migrated from Silverstripe CMS 3.x may be put to the default "/Uploads" folder instead. This affects installations which allowed upload folder protection via the optional silverstripe/secureassets module under 3.x. This module is installed and enabled by default on the Common Web Platform (CWP). The vulnerability only affects files uploaded after an upgrade to 4.x.
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Analysis
by VulDB Data Team • 04/16/2020
The vulnerability described in CVE-2020-9280 represents a critical access control flaw within SilverStripe CMS versions up to 4.5 that stems from improper handling of file upload permissions during migration processes from version 3.x to 4.x. This issue specifically impacts installations that utilize the silverstripe/secureassets module, which was automatically enabled in the Common Web Platform environment, creating a significant security risk for organizations relying on proper file access controls. The flaw manifests when files are uploaded through forms to folders that were migrated from SilverStripe CMS 3.x environments, where the security context and access controls are not properly maintained during the upgrade process.
The technical root cause of this vulnerability lies in the improper migration of upload folder permissions and access controls from the legacy 3.x system to the newer 4.x framework. When SilverStripe CMS 3.x installations were upgraded to version 4.x, the system failed to correctly preserve the folder protection mechanisms that were in place in the older version. This results in files that should remain restricted to specific user groups or access levels being placed into the default "/Uploads" folder, which typically has more permissive access controls. The vulnerability specifically affects files uploaded after the upgrade process, indicating that pre-existing files in the migrated system maintain their original security context while new uploads are subject to the flawed permission handling.
From an operational impact perspective, this vulnerability creates a serious risk for organizations that depend on controlled file access within their SilverStripe installations. The default "/Uploads" folder typically lacks the granular access controls that were present in the original 3.x protected folders, potentially allowing unauthorized users to access sensitive documents, media files, or other uploaded content that should remain restricted. This flaw directly violates the principle of least privilege and can lead to data exposure incidents, particularly in environments where the silverstripe/secureassets module was intended to provide enhanced security for file uploads. The vulnerability affects installations that were upgraded from 3.x to 4.x, meaning that fresh installations or those that never migrated from 3.x are not affected by this specific issue.
Security professionals should note that this vulnerability aligns with CWE-276, which addresses improper file permissions, and relates to ATT&CK technique T1078.004 for valid accounts and T1566 for phishing attacks that could exploit the reduced access controls. Organizations should implement immediate mitigations including verifying that all migrated folders maintain their intended access controls, reviewing the configuration of the silverstripe/secureassets module, and ensuring that file upload folders are properly secured in the upgraded environment. The recommended approach involves conducting a comprehensive audit of all upload folders post-migration, reconfiguring any improperly migrated folders to maintain their original security context, and implementing proper access control validation for all new file uploads. Additionally, organizations should consider disabling or properly configuring the secureassets module to prevent future occurrences of this type of access control regression during software upgrades.