CVE-2018-9921 in CMS Made Simple
Summary
by MITRE
In CMS Made Simple 2.2.7, a Directory Traversal issue makes it possible to determine the existence of files and directories outside the web-site installation directory, and determine whether a file has contents matching a specified checksum. The attack uses an admin/checksum.php?__c= request.
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Analysis
by VulDB Data Team • 01/30/2020
The vulnerability identified as CVE-2018-9921 affects CMS Made Simple version 2.2.7 and represents a critical directory traversal flaw that exposes sensitive system information through improper input validation. This weakness allows unauthorized attackers to enumerate files and directories beyond the intended web root, potentially revealing critical system artifacts and application structure information. The vulnerability specifically manifests through the admin/checksum.php endpoint where the __c parameter is improperly handled, creating an attack vector that bypasses normal access controls and file system boundaries.
The technical implementation of this vulnerability stems from inadequate sanitization of user-supplied input parameters within the checksum verification functionality. When an attacker crafts a malicious request to admin/checksum.php with a specially formatted __c parameter, the application fails to properly validate or restrict the file path traversal attempts. This flaw aligns with CWE-22, which classifies improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The vulnerability enables attackers to perform reconnaissance activities that can reveal system configurations, file structures, and potentially sensitive data that should remain protected within the application's designated boundaries.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the ability to verify file existence and determine content checksums for files outside the web root directory. This capability significantly increases the attack surface by enabling threat actors to map the underlying file system structure and identify potentially vulnerable components or sensitive files that may contain credentials, configuration data, or other exploitable resources. Attackers can leverage this information to plan more sophisticated attacks, potentially leading to privilege escalation, remote code execution, or complete system compromise depending on the discovered file contents and system permissions.
Security professionals should implement immediate mitigations including patching the application to the latest version where this vulnerability has been addressed, implementing proper input validation and sanitization for all user-supplied parameters, and restricting access to administrative endpoints through network segmentation and authentication controls. The vulnerability demonstrates the critical importance of proper access control mechanisms and input validation in web applications, aligning with ATT&CK technique T1083 for discovering system information and T1566 for credential access through reconnaissance activities. Organizations should also consider implementing web application firewalls to detect and block suspicious traversal patterns, while conducting regular security assessments to identify similar vulnerabilities in other components of their web infrastructure.