CVE-2018-18572 in osCommerce
Summary
by MITRE
osCommerce 2.3.4.1 has an incomplete '.htaccess' for blacklist filtering in the "product" page. Because of this filter, script files with certain PHP-related extensions (such as .phtml and .php5) didn't execute in the application. But this filter didn't prevent the '.pht' extension. Thus, remote authenticated administrators can upload '.pht' files for arbitrary PHP code execution via a /catalog/admin/categories.php?cPath=&action=new_product URI.
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Analysis
by VulDB Data Team • 12/01/2023
The vulnerability identified as CVE-2018-18572 affects osCommerce version 2.3.4.1 and represents a critical authorization bypass and remote code execution flaw within the administrative interface. This issue stems from an incomplete security configuration in the application's .htaccess file that was designed to prevent execution of potentially malicious PHP scripts. The security mechanism was intended to block script files with extensions such as .phtml and .php5, which are commonly associated with PHP execution contexts. However, the implementation contained a significant oversight that allowed attackers to bypass the intended restrictions through the use of the .pht file extension.
The technical flaw manifests in the administrative product creation functionality where authenticated administrators can upload files with the .pht extension through the specific URI path /catalog/admin/categories.php?cPath=&action=new_product. This particular extension was not included in the blacklist filtering mechanism, creating a pathway for arbitrary code execution. The .pht extension is less commonly recognized as a PHP execution context, making it an effective vector for exploitation as it bypasses the security controls that were designed to prevent such attacks. This vulnerability directly relates to CWE-174, which describes insufficient blacklist filtering or overly permissive file type validation, and represents a classic case of incomplete input validation.
The operational impact of this vulnerability is severe as it allows remote authenticated administrators to execute arbitrary PHP code on the target system. This means that an attacker with valid administrative credentials can upload malicious files that will be executed with the privileges of the web server, potentially leading to complete system compromise. The attack requires only administrative access, which is often obtained through other means such as credential theft or social engineering, making this vulnerability particularly dangerous. The exploit chain involves uploading a .pht file containing malicious PHP code and then accessing it through the vulnerable administrative interface, which aligns with ATT&CK technique T1505.003 for 'Malicious File' and T1078.004 for 'Valid Accounts' in the context of privilege escalation.
The vulnerability demonstrates a critical flaw in the application's defense-in-depth strategy, where a single point of failure in the access control mechanism allows for arbitrary code execution. The incomplete .htaccess configuration represents a failure in proper security hardening and input validation practices, as it relies on a hardcoded list of extensions rather than implementing more robust security measures such as whitelisting or content-based validation. Organizations using osCommerce 2.3.4.1 should immediately implement patches or workarounds that either properly blacklist the .pht extension or implement additional access controls. The fix should ensure that all potential PHP execution contexts are properly filtered, and that file upload mechanisms are properly validated against a comprehensive whitelist of allowed extensions rather than relying on incomplete blacklist approaches. This vulnerability serves as a reminder of the importance of thorough security testing and the dangers of incomplete access control implementations.