CVE-2016-10836 in cPanel
Summary
by MITRE
cPanel before 55.9999.141 allows arbitrary file-read operations during authentication with caldav (SEC-108).
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Analysis
by VulDB Data Team • 11/20/2023
The vulnerability identified as CVE-2016-10836 represents a critical security flaw in cPanel versions prior to 55.9999.141 that enables unauthorized file read operations during caldav authentication processes. This vulnerability specifically targets the calendar and scheduling components of cPanel's web-based control panel system, which is widely deployed across hosting environments and enterprise web servers. The flaw occurs within the authentication mechanism that handles caldav protocol requests, allowing malicious actors to exploit improper access controls and bypass authentication barriers to read arbitrary files on the affected system. The security implications are severe as this vulnerability can potentially expose sensitive configuration files, user data, and system information that should remain protected behind proper authentication boundaries.
The technical root cause of this vulnerability stems from inadequate input validation and access control implementation within the caldav authentication pathway. When cPanel processes caldav requests, it fails to properly sanitize file paths or validate user permissions before attempting to read files from the server filesystem. This weakness creates a directory traversal or path traversal condition that can be exploited by attackers to access files outside of the intended caldav data directories. The vulnerability operates at the application layer and can be triggered through crafted caldav requests that manipulate file path parameters. According to CWE classification, this vulnerability maps to CWE-22 Path Traversal and CWE-285 Improper Authorization, both of which are fundamental security weaknesses that directly enable unauthorized access to system resources.
The operational impact of CVE-2016-10836 extends beyond simple information disclosure, as it provides attackers with the capability to extract sensitive data that could be leveraged for further exploitation. An attacker who successfully exploits this vulnerability can access configuration files containing database credentials, encryption keys, and other system information that would typically remain protected. This access could enable privilege escalation attacks, facilitate additional reconnaissance, or provide the necessary information to compromise the entire hosting environment. The vulnerability affects cPanel installations across various hosting providers and enterprise deployments where calendar and scheduling functionality is enabled, making it a widespread concern for organizations maintaining web server infrastructure. The attack vector requires minimal privileges as the vulnerability can be exploited during the authentication process itself, meaning that even unauthenticated users may be able to perform file read operations.
Mitigation strategies for this vulnerability primarily focus on immediate patching of affected cPanel installations to version 55.9999.141 or later, which contains the necessary security fixes. Organizations should also implement network-level restrictions to limit access to caldav endpoints and consider disabling unnecessary calendar services when not actively required. Additional defensive measures include implementing proper file access controls, monitoring for unusual file access patterns, and conducting regular security assessments of web applications. The vulnerability demonstrates the importance of proper authentication and authorization mechanisms, aligning with ATT&CK technique T1078 Valid Accounts and T1566 Phishing, as attackers could potentially use the information gained to escalate privileges or conduct further attacks. Security teams should also consider implementing web application firewalls and intrusion detection systems to monitor for exploitation attempts targeting this specific vulnerability pattern. Organizations with legacy cPanel installations should prioritize upgrading to patched versions while maintaining comprehensive monitoring of their systems for any signs of unauthorized access or file read operations.