CVE-2017-18388 in cPanel
Summary
by MITRE
cPanel before 68.0.15 can perform unsafe file operations because Jailshell does not set the umask (SEC-315).
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 07/18/2020
The vulnerability identified as CVE-2017-18388 affects cPanel versions prior to 68.0.15 and stems from an insecure file operation within the Jailshell component. This flaw represents a critical security oversight that undermines the integrity of user file permissions and system security boundaries. The issue specifically manifests when Jailshell fails to properly configure the umask parameter, which is essential for establishing appropriate default file permissions during file creation operations. Without proper umask configuration, newly created files and directories inherit default permissions that may be excessively permissive, potentially exposing sensitive system resources to unauthorized access. This vulnerability directly impacts the principle of least privilege and can lead to privilege escalation scenarios where malicious actors gain elevated system access through manipulated file permissions.
The technical root cause of this vulnerability lies in the improper implementation of umask settings within the Jailshell environment. Umask values control the default permissions for newly created files and directories by specifying which permission bits should be excluded from the default permissions. When Jailshell does not set the umask correctly, it allows files to be created with overly permissive default permissions, typically resulting in world-readable or world-writable files. This behavior violates fundamental security practices and creates opportunities for attackers to exploit the system through file manipulation attacks. The vulnerability aligns with CWE-276, which addresses improper default permissions, and represents a specific instance of insecure file handling within restricted shell environments. From an operational perspective, this flaw can be exploited by attackers who gain access to user accounts or compromised services to manipulate file permissions and potentially escalate privileges within the cPanel environment.
The operational impact of CVE-2017-18388 extends beyond simple file permission issues to encompass broader system compromise possibilities. Attackers can leverage this vulnerability to create files with unintended permissions, potentially allowing them to overwrite critical system files, establish persistent backdoors, or access sensitive user data. The vulnerability affects all cPanel installations running versions earlier than 68.0.15, making it particularly concerning given the widespread adoption of cPanel in web hosting environments. Organizations using affected versions face increased risk of data breaches, system compromise, and unauthorized access to customer data stored on servers. The attack surface is particularly broad since cPanel serves as a primary interface for many hosting providers, making this vulnerability a significant concern for the hosting industry. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and persistence, as attackers can manipulate file permissions to maintain access and execute malicious code within the compromised environment.
Mitigation strategies for CVE-2017-18388 primarily focus on upgrading to cPanel version 68.0.15 or later, which contains the necessary patches to properly configure umask settings within Jailshell. System administrators should prioritize immediate deployment of the security update to eliminate the vulnerability. Additionally, organizations should conduct comprehensive audits of their cPanel installations to identify any remaining vulnerable systems and ensure proper umask configuration across all shell environments. Network segmentation and access controls should be implemented to limit potential attack vectors, while monitoring systems should be configured to detect unusual file creation patterns that might indicate exploitation attempts. Security teams should also review and harden default file permissions across the entire system, ensuring that proper umask values are enforced throughout the environment. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other software components and maintain overall system security posture. The vulnerability serves as a reminder of the critical importance of proper permission management in restricted shell environments and highlights the need for regular security updates and patch management processes.