CVE-2017-18428 in cPanel
Summary
by MITRE
In cPanel before 66.0.2, Apache HTTP Server domlogs become temporarily world-readable during log processing (SEC-290).
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Analysis
by VulDB Data Team • 07/18/2020
The vulnerability identified as CVE-2017-18428 affects cPanel versions prior to 66.0.2 and relates to a critical security flaw in the Apache HTTP Server domlogs processing mechanism. This issue represents a privilege escalation and information disclosure vulnerability that can potentially allow unauthorized access to sensitive web server log data. The flaw manifests during the routine log processing operations that cPanel performs to maintain web server statistics and monitoring capabilities. When cPanel processes domain logs, it temporarily sets world-readable permissions on these log files, creating a window of opportunity for malicious actors to access potentially sensitive information contained within the web server logs. This vulnerability falls under the CWE-276 category of insecure default permissions, where the system fails to properly restrict access to sensitive files during processing operations. The security implications extend beyond simple information disclosure as these logs may contain user session data, authentication attempts, application errors, and other sensitive operational information that could be exploited by attackers to gain deeper insights into the target system. During the log processing window, any user with basic system access or network connectivity could potentially read these temporary world-readable files, creating an attack surface that violates fundamental security principles of least privilege and proper file access control.
The technical implementation of this vulnerability stems from how cPanel handles the temporary file permissions during domlog processing operations. When cPanel processes web server logs, it creates temporary files or modifies existing log file permissions to allow the processing utilities to access the data. However, the implementation fails to properly reset these permissions to restrictive settings after processing completes. This creates a race condition where the log files remain world-readable for a brief period, typically during the processing window. The vulnerability is particularly concerning because it operates within the legitimate system processes that administrators expect to run without security concerns. Attackers can exploit this timing window to harvest sensitive data including but not limited to user agent strings, IP addresses, request parameters, and potentially session identifiers. The flaw demonstrates poor security hygiene in file permission management and highlights the importance of proper privilege separation in system operations. According to ATT&CK framework, this vulnerability aligns with technique T1083 (File and Directory Discovery) and T1566 (Phishing) as attackers could use the harvested information to craft more targeted attacks or gain additional system access through reconnaissance.
The operational impact of CVE-2017-18428 extends beyond immediate data exposure to encompass broader security implications for web hosting environments. Organizations running affected cPanel versions face potential compromise of user privacy, application security, and system integrity. The temporary nature of the vulnerability means that defenders must maintain constant vigilance during log processing windows, which can be challenging to monitor effectively. This vulnerability particularly affects shared hosting environments where multiple customers' data may be exposed through a single compromised log file. The exposure of web server logs can reveal sensitive information about application behavior, user activities, and system vulnerabilities that could be leveraged in subsequent attacks. Additionally, the vulnerability impacts compliance requirements for organizations subject to data protection regulations such as GDPR, HIPAA, or PCI-DSS, where unauthorized access to log data could constitute a compliance violation. The timing of the vulnerability means that it could be exploited by automated scanning tools or manual reconnaissance efforts, making it a persistent threat to systems that do not have proper patch management procedures in place. Organizations should consider implementing monitoring solutions to detect unauthorized access to log files during processing windows and establish incident response procedures specifically addressing this type of vulnerability.
The recommended mitigation strategy for CVE-2017-18428 involves immediate deployment of cPanel version 66.0.2 or later, which contains the necessary patches to address the file permission handling during log processing. System administrators should also implement additional monitoring controls to detect unauthorized access attempts to log files during processing windows, utilizing audit tools and log analysis systems to track file access patterns. Organizations should review their file permission policies and implement automated checks to ensure that sensitive files do not remain world-readable during processing operations. The patch addresses the root cause by properly managing file permissions throughout the entire processing lifecycle, ensuring that temporary permissions are properly reset to restrictive settings immediately after processing completes. Security teams should also consider implementing network segmentation and access controls to limit exposure of log processing systems to unauthorized users. Regular vulnerability assessments should include checks for similar permission handling issues in other system components, as this type of vulnerability represents a common security pattern that can occur in various software applications. The fix demonstrates the importance of proper privilege management in system operations and highlights the need for security testing of file permission handling in routine system processes, particularly those that involve sensitive data processing.