CVE-2017-18403 in cPanel
Summary
by MITRE
cPanel before 68.0.15 allows code execution in the context of the nobody account via Mailman archives (SEC-337).
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Analysis
by VulDB Data Team • 07/18/2020
The vulnerability identified as CVE-2017-18403 represents a critical code execution flaw in cPanel versions prior to 68.0.15, specifically affecting the Mailman mailing list management component. This security issue arises from improper input validation and handling within the Mailman archive functionality, creating a pathway for arbitrary code execution under the privileges of the nobody account. The vulnerability is particularly concerning as it operates within the context of a low-privilege user account while still enabling full code execution capabilities, making it a significant vector for privilege escalation and system compromise.
The technical flaw stems from inadequate sanitization of user-supplied data within the Mailman archive processing module. When users interact with Mailman archives, the system fails to properly validate and sanitize input parameters, allowing maliciously crafted data to be processed without proper security checks. This vulnerability falls under CWE-20, which specifically addresses improper input validation, and represents a classic example of a command injection or code execution vulnerability. The issue manifests when the system processes archived mailing list content, where user-controllable variables are directly incorporated into system commands or interpreted as executable code without proper escaping or validation mechanisms.
The operational impact of this vulnerability extends beyond simple code execution, as it enables attackers to leverage the nobody account context to perform actions that could compromise entire server environments. The nobody account typically has minimal privileges but still maintains access to system resources and processes that could be exploited for further compromise. Attackers could potentially use this vulnerability to execute arbitrary commands, access sensitive data, modify system configurations, or establish persistent access to the compromised system. This vulnerability particularly affects shared hosting environments where cPanel is commonly deployed, making it a significant concern for hosting providers and their customers who rely on Mailman for mailing list management.
Mitigation strategies for CVE-2017-18403 primarily focus on immediate remediation through cPanel version updates to 68.0.15 or later, which contain the necessary patches to address the input validation flaws. Organizations should also implement network-level restrictions to limit access to Mailman functionality where possible, particularly by restricting direct access to Mailman archive interfaces. Additionally, security monitoring should be enhanced to detect unusual patterns in Mailman archive processing or unexpected code execution attempts. The vulnerability aligns with ATT&CK technique T1059, which covers command and scripting interpreter, and T1068, which addresses exploit for privilege escalation, making it particularly relevant for organizations implementing comprehensive threat detection and response strategies. System administrators should also consider implementing application whitelisting policies and ensuring proper input validation is enforced across all Mailman-related components to prevent similar vulnerabilities from emerging in the future.