CVE-2018-10519 in CMS Made Simple
Summary
by MITRE
CMS Made Simple (CMSMS) 2.2.7 contains a privilege escalation vulnerability from ordinary user to admin user by arranging for the eff_uid value within $_COOKIE[$this->_loginkey] to equal 1, because files in the tmp/ directory are accessible through HTTP requests. NOTE: this vulnerability exists because of an incorrect fix for CVE-2018-10084.
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Analysis
by VulDB Data Team • 02/01/2020
The vulnerability identified as CVE-2018-10519 represents a critical privilege escalation flaw within CMS Made Simple version 2.2.7 that allows ordinary users to elevate their privileges to administrative status. This vulnerability specifically exploits the authentication mechanism by manipulating the eff_uid value within the $_COOKIE[$this->_loginkey] variable to equal 1, which typically represents the administrator user account in CMSMS systems. The flaw stems from an improper implementation of a previous security fix for CVE-2018-10084, creating a regression that undermines the intended security controls.
The technical exploitation of this vulnerability occurs through the accessibility of temporary files within the tmp/ directory through HTTP requests. This misconfiguration allows attackers to manipulate cookie values that are stored in temporary files, effectively bypassing the normal authentication checks that should prevent non-administrative users from accessing administrative functions. The vulnerability operates at the application layer and leverages the weakness in how CMSMS handles user session management and privilege verification. According to CWE-284, this represents an improper access control vulnerability where the system fails to properly enforce authorization mechanisms.
The operational impact of this privilege escalation vulnerability is severe as it enables attackers to gain complete administrative control over affected CMSMS installations. Once elevated to admin status, attackers can modify or delete content, install malicious plugins, access sensitive user data, modify system configurations, and potentially use the compromised system as a launchpad for further attacks within the network. The vulnerability is particularly dangerous because it requires no special privileges to exploit, making it accessible to any user who can interact with the CMSMS application. This aligns with ATT&CK technique T1078 which covers valid accounts and credential access, though in this case the vulnerability allows for unauthorized privilege escalation rather than legitimate credential theft.
The root cause of this vulnerability lies in the insecure handling of temporary files and the flawed implementation of authentication state management. The tmp/ directory should never be accessible through HTTP requests as it typically contains session data, temporary files, and other sensitive information that could be exploited by attackers. The improper fix for CVE-2018-10084 created a new attack vector by failing to properly secure the temporary file storage mechanism while attempting to address the previous vulnerability. Organizations running CMSMS 2.2.7 should immediately implement mitigations including restricting HTTP access to the tmp/ directory, ensuring proper file permissions, and applying the official security patches released by CMSMS developers. The vulnerability demonstrates the importance of thorough testing of security patches and the potential for regression vulnerabilities when addressing security issues.