CVE-2018-20927 in cPanel
Summary
by MITRE
cPanel before 70.0.23 allows jailshell escape because of incorrect crontab parsing (SEC-382).
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Analysis
by VulDB Data Team • 07/18/2020
The vulnerability identified as CVE-2018-20927 represents a critical security flaw in cPanel versions prior to 70.0.23 that enables unauthorized jailshell escape through improper crontab parsing mechanisms. This vulnerability specifically targets the security boundaries that protect users within the cPanel environment, potentially allowing malicious actors to break out of restricted user environments and gain elevated privileges. The issue stems from how cPanel handles cron job parsing and execution within the jailshell context, creating an exploitable condition that undermines the fundamental security model of the platform.
The technical implementation of this vulnerability involves a flaw in the crontab parsing logic where cPanel fails to properly validate or sanitize cron job entries that could contain malicious payloads. When users create cron jobs within their jailshell environment, the system does not adequately verify the integrity of these entries before processing them, allowing for potential command injection or privilege escalation attacks. This parsing error creates a pathway where attackers can manipulate cron job definitions to execute arbitrary commands outside of the intended restricted environment, effectively bypassing the security controls designed to contain user activities.
The operational impact of CVE-2018-20927 extends beyond simple privilege escalation, as it fundamentally compromises the security architecture of cPanel installations. Organizations relying on cPanel for hosting services face significant risks including unauthorized access to multiple user accounts, potential data breaches, and complete system compromise. The vulnerability enables attackers to execute commands with elevated privileges, potentially leading to full system control, data exfiltration, or the establishment of persistent backdoors within the hosting environment. This risk is particularly severe in shared hosting environments where multiple customers share the same infrastructure.
Mitigation strategies for this vulnerability require immediate patching to cPanel version 70.0.23 or later, which contains the necessary fixes for the crontab parsing implementation. System administrators should also implement additional monitoring of cron job activities and user account behaviors to detect potential exploitation attempts. The remediation process involves verifying that all affected cPanel installations have been updated and that proper access controls remain in place. Organizations should conduct comprehensive security assessments of their hosting environments to identify any potential compromise and ensure that proper incident response procedures are in place to address similar vulnerabilities in the future.
This vulnerability aligns with CWE-78 and CWE-20 categories, representing command injection flaws and input validation issues respectively, while also mapping to ATT&CK techniques related to privilege escalation and persistence within hosting environments. The flaw demonstrates the critical importance of proper input validation and the potential consequences when security boundaries are improperly enforced in shared hosting platforms.