CVE-2016-10857 in cPanel
Summary
by MITRE
cPanel before 11.54.0.0 allows a bypass of the e-mail sending limit (SEC-60).
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Analysis
by VulDB Data Team • 11/20/2023
The vulnerability identified as CVE-2016-10857 represents a critical security flaw in cPanel versions prior to 11.54.0.0 that enables unauthorized bypass of email sending limits. This issue falls under the category of privilege escalation and access control bypass, where legitimate users can circumvent the built-in email throttling mechanisms that are designed to prevent spamming and abuse of the email infrastructure. The vulnerability specifically targets the email sending limit enforcement system that cPanel implements to manage email traffic and maintain server stability.
The technical flaw resides in the email queue management and rate limiting implementation within cPanel's email handling subsystem. When users exceed the configured email sending limits, the system should normally restrict further email transmission until the limit resets or is manually adjusted. However, this vulnerability allows malicious actors or authorized users with sufficient privileges to manipulate the email sending process, effectively bypassing these protective measures. The flaw likely stems from improper validation of email sending requests or inadequate state tracking of email queue submissions that should be monitored against established limits.
The operational impact of this vulnerability is significant for system administrators and hosting providers who rely on cPanel for managing email services. When exploited, attackers can flood email servers with excessive messages, potentially leading to service degradation, denial of service conditions, and violation of anti-spam policies that hosting providers must maintain. This bypass capability can result in legitimate email services being disrupted while simultaneously enabling spam campaigns or malicious email distribution. The vulnerability also creates potential compliance issues for organizations that must adhere to email sending quotas and anti-abuse policies required by internet service providers and regulatory bodies.
Organizations affected by this vulnerability should immediately upgrade to cPanel version 11.54.0.0 or later, which contains the necessary patches to address the email sending limit bypass issue. System administrators should also implement additional monitoring of email sending activities to detect unusual patterns that might indicate exploitation attempts. The mitigation strategy should include reviewing current email sending limits and ensuring that proper logging and alerting mechanisms are in place to monitor for potential abuse. This vulnerability demonstrates the importance of maintaining up-to-date software versions and the critical role that email rate limiting plays in preventing abuse of shared hosting environments. The issue aligns with CWE-284, which addresses improper access control, and may relate to ATT&CK techniques involving privilege escalation and abuse of cloud platforms. Organizations should also consider implementing additional email security measures such as SPF, DKIM, and DMARC configurations to provide layered protection against email abuse.