CVE-2016-10833 in cPanel
Summary
by MITRE
cPanel before 55.9999.141 mishandles username-based blocking for PRE requests in cPHulkd (SEC-104).
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Analysis
by VulDB Data Team • 11/20/2023
The vulnerability identified as CVE-2016-10833 affects cPanel versions prior to 55.9999.141 and specifically relates to improper handling of username-based blocking mechanisms within the cPHulkd service. This issue represents a significant security flaw in the authentication and access control systems of cPanel installations, which could potentially allow unauthorized access or denial of service attacks against legitimate users. The vulnerability manifests in how cPHulkd processes PRE requests, which are typically part of the authentication workflow used by cPanel to manage user access and session handling.
The technical flaw stems from inadequate validation and processing of username-based blocking logic during PRE request handling within the cPHulkd daemon. This daemon is responsible for implementing brute force protection and account locking mechanisms that prevent unauthorized access attempts. When cPanel processes PRE requests for username validation, the system fails to properly enforce the blocking rules that should prevent excessive login attempts from specific usernames. This misconfiguration allows attackers to bypass the intended security controls, potentially enabling them to perform credential stuffing attacks or continued brute force attempts against specific user accounts without proper rate limiting or account blocking enforcement.
The operational impact of this vulnerability extends beyond simple authentication bypasses, as it undermines the fundamental security controls that protect cPanel installations from automated attack vectors. Attackers could exploit this flaw to systematically target specific user accounts, potentially leading to account compromise or service disruption. The vulnerability affects the integrity of the authentication system and could result in unauthorized access to sensitive administrative functions, user data, or system resources. Organizations using affected cPanel versions may experience increased risk of successful brute force attacks, credential theft, and potential privilege escalation opportunities for malicious actors.
Mitigation strategies should prioritize immediate patching of affected cPanel installations to version 55.9999.141 or later, which contains the necessary fixes for the username-based blocking mechanism in cPHulkd. System administrators should also implement additional monitoring and logging of authentication attempts to detect anomalous behavior patterns that may indicate exploitation attempts. Network-level controls such as iptables rules or firewall configurations can be deployed to limit login attempts from specific IP addresses or ranges. Organizations should also review their existing security policies and ensure proper account lockout mechanisms are in place, while considering the implementation of multi-factor authentication to add additional layers of protection. The vulnerability aligns with CWE-307, which addresses improper restriction of repeated authentication attempts, and could potentially map to ATT&CK technique T1110 for credential stuffing attacks and T1499 for denial of service through resource exhaustion.