CVE-2017-18475 in cPanel
Summary
by MITRE
In cPanel before 62.0.4, Exim piped filters ran in the context of an incorrect user account when delivering to a system user (SEC-204).
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Analysis
by VulDB Data Team • 07/21/2020
The vulnerability identified as CVE-2017-18475 represents a critical privilege escalation issue within the cPanel control panel ecosystem that affected versions prior to 62.0.4. This flaw specifically impacted the Exim mail transfer agent configuration within cPanel's piped filter delivery mechanism, creating a scenario where system-level mail processing operations executed under incorrect user permissions. The vulnerability stems from improper privilege management during the mail delivery process, where the system failed to maintain proper user context when routing emails through piped filters to system users.
The technical implementation of this vulnerability involves the Exim mail system's piped filter functionality, which allows administrators to define custom mail processing rules that execute external programs or scripts. When cPanel processed mail deliveries to system users through these piped filters, it incorrectly set the execution context to a different user account than intended. This misconfiguration creates a path for privilege escalation attacks where malicious actors could potentially execute code with elevated privileges beyond what their original user account should have access to. The flaw operates at the intersection of mail delivery configuration and user privilege management, creating an environment where system-level operations can be hijacked by unauthorized users.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential data compromise and system compromise scenarios. Attackers exploiting this vulnerability could gain access to system user mail accounts, potentially accessing sensitive email communications, system configuration files, and other data that should remain restricted to authorized personnel. The vulnerability particularly affects environments where cPanel manages multiple user accounts and where piped filters are configured for automated mail processing. Organizations running affected cPanel versions face significant risk of unauthorized access to mail systems, potential lateral movement within network environments, and possible complete system compromise if attackers can leverage the elevated privileges to access system resources.
Mitigation strategies for CVE-2017-18475 primarily focus on immediate remediation through cPanel version updates to 62.0.4 or later, which contain the necessary patches to correct the privilege context handling in Exim piped filters. Security administrators should also conduct thorough audits of existing piped filter configurations to identify and disable unnecessary or potentially risky mail processing rules. The vulnerability aligns with CWE-276, which addresses improper privilege management, and relates to ATT&CK technique T1068, which covers exploit for privilege escalation. Organizations should implement monitoring solutions to detect anomalous mail processing activities and establish robust patch management procedures to ensure timely deployment of security updates. Additionally, implementing principle of least privilege for mail processing accounts and regular security assessments of mail system configurations will help reduce the attack surface and prevent exploitation of similar privilege escalation vulnerabilities in the future.