CVE-2016-10816 in cPanel
Summary
by MITRE
cPanel before 57.9999.54 allows Webmail accounts to execute arbitrary code through forwarders (SEC-121).
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 11/14/2023
The vulnerability identified as CVE-2016-10816 represents a critical arbitrary code execution flaw within cPanel software versions prior to 57.9999.54. This security weakness specifically affects Webmail accounts and exploits a vulnerability in the forwarder functionality, which is a common email management feature that allows users to automatically redirect incoming emails to other email addresses. The vulnerability was classified as SEC-121 by cPanel's security team, indicating its severity and the need for immediate remediation. The flaw stems from inadequate input validation and sanitization within the forwarder configuration processing, creating a pathway for malicious actors to inject and execute arbitrary commands on the affected system. This type of vulnerability falls under the CWE-74 category of Improper Neutralization of Special Elements in Output Used by a Downstream Component, specifically within the context of email forwarding mechanisms where user input is not properly sanitized before being processed by the system.
The technical exploitation of this vulnerability occurs when a malicious Webmail account user manipulates the forwarder configuration to include malicious code within the forwarding address or related parameters. The vulnerability allows attackers to leverage the forwarder functionality to execute arbitrary commands with the privileges of the web server process, potentially leading to complete system compromise. This occurs because the system fails to properly validate or sanitize user-supplied data before using it in system commands or configuration updates. The attack vector specifically targets the webmail interface where users can configure email forwarders, making it accessible through standard web browser interactions without requiring elevated privileges beyond basic user access. The flaw demonstrates a classic command injection vulnerability where user-controllable input is directly incorporated into system commands without proper sanitization, enabling attackers to execute arbitrary shell commands on the server hosting the cPanel instance.
The operational impact of this vulnerability extends beyond simple privilege escalation, potentially allowing attackers to gain full control over the compromised cPanel server and all associated services. An attacker who successfully exploits this vulnerability can execute commands with the privileges of the web server process, which typically runs with elevated permissions to manage email services and system configurations. This could lead to data exfiltration, system compromise, and unauthorized access to other users' email accounts and data stored on the server. The vulnerability affects organizations relying on cPanel for web hosting management, potentially exposing thousands of websites and email accounts to unauthorized access. The impact is particularly severe for shared hosting environments where multiple customers share the same server infrastructure, as a successful exploitation could allow attackers to access other customers' data and potentially pivot to compromise additional systems within the network. The vulnerability also impacts compliance with security standards such as pci dss and soc 2, as it creates potential data breaches and unauthorized access scenarios that violate regulatory requirements for data protection and system security.
Organizations should immediately implement the remediation measures provided by cPanel, including updating to version 57.9999.54 or later, which contains the necessary patches to address the forwarder input validation issues. System administrators should also implement additional security controls such as monitoring for unusual forwarder configurations, implementing web application firewalls to detect and block malicious input patterns, and conducting regular security assessments of email configurations. The vulnerability demonstrates the importance of proper input validation and sanitization in web applications, aligning with security best practices outlined in the owasp top ten and other industry standards. Organizations should also consider implementing principle of least privilege for webmail accounts and regularly audit forwarder configurations to detect any unauthorized modifications. The incident underscores the critical need for continuous security monitoring and prompt patch management, as delays in applying security updates can leave systems vulnerable to exploitation by threat actors who actively scan for and exploit known vulnerabilities. This vulnerability serves as a reminder of the importance of maintaining up-to-date security patches and implementing comprehensive security monitoring across all system components, particularly those handling user input in web applications.