CVE-2020-5295: 
PHP vulnerability analysis and mitigation

CVE-2020-5295 is a local file inclusion vulnerability affecting OctoberCMS (october/october composer package) versions from 1.0.319 and before 1.0.466. The vulnerability allows authenticated backend users with 'cms.manage_assets' permission to read local files on the October CMS server through the asset management functionality (GitHub Advisory).

The vulnerability exists in the asset editing functionality, specifically in the index_onOpenTemplate() function defined in modules/cms/controllers/Index.php. The function initializes the template variable directly using the 'path' parameter without proper validation, allowing an attacker to retrieve contents of any file on the server. The issue was patched in Build 466 by improving asset file path handling to limit paths to those under the assets directory (GitHub Commit).

An authenticated attacker with 'cms.manage_assets' permission can read sensitive local files on the October CMS server, potentially exposing configuration files, credentials, and other confidential information (Full Disclosure).

The vulnerability requires authentication and specific permissions ('cms.manage_assets') to exploit. An attacker can exploit this by modifying the 'path' parameter in requests that retrieve assets for editing, allowing them to read arbitrary files on the server. A proof-of-concept exploit has been published that demonstrates the ability to retrieve any file from October CMS when provided with the appropriate user cookies (Full Disclosure).

The primary mitigation is to upgrade to OctoberCMS version 1.0.466 or later, which includes the security patch. For users unable to upgrade, a manual workaround is available by applying the patch from commit 2b8939c, which implements proper validation of the asset file paths (GitHub Advisory).