CVE-2020-29136 in cPanel
Summary
by MITRE • 11/27/2020
In cPanel before 90.0.17, 2FA can be bypassed via a brute-force approach (SEC-575).
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Analysis
by VulDB Data Team • 12/10/2020
The vulnerability identified as CVE-2020-29136 represents a critical security flaw in cPanel software versions prior to 90.0.17 that allows unauthorized users to bypass two-factor authentication mechanisms through brute-force attacks. This weakness directly undermines the security posture of systems relying on cPanel for web hosting management and administration. The vulnerability stems from insufficient rate limiting and authentication controls that fail to properly detect and prevent repeated authentication attempts, creating a pathway for malicious actors to systematically guess valid authentication tokens or codes.
The technical implementation of this vulnerability involves the absence of effective countermeasures against automated credential guessing attacks. In properly secured systems, multiple failed authentication attempts should trigger protective mechanisms such as account lockouts, temporary IP blocking, or exponential backoff delays. However, cPanel versions before 90.0.17 lacked these essential protections, enabling attackers to perform brute-force operations against the two-factor authentication system without sufficient resistance. This flaw operates at the authentication layer and can be categorized under CWE-307, which addresses inadequate protection against brute-force attacks. The vulnerability specifically impacts the authentication flow where users are expected to provide both primary credentials and secondary factor verification, creating a window of opportunity for attackers to exploit the system's lack of proper throttling mechanisms.
The operational impact of this vulnerability extends beyond simple unauthorized access to potentially compromise entire hosting environments. When two-factor authentication is bypassed, attackers gain elevated privileges that could enable them to modify website content, access sensitive customer data, manipulate server configurations, or establish persistent backdoors. This risk is particularly severe in shared hosting environments where multiple customers' data resides on the same infrastructure. The vulnerability aligns with ATT&CK technique T1110.003, which covers credential guessing through brute force methods, and can facilitate subsequent attacks such as privilege escalation and lateral movement within the compromised system. Organizations using vulnerable cPanel versions face significant exposure to data breaches, service disruption, and regulatory compliance violations that could result in substantial financial and reputational damage.
Mitigation strategies for this vulnerability require immediate implementation of cPanel version 90.0.17 or later, which includes enhanced authentication controls and rate limiting features. System administrators should also implement additional protective measures such as configuring fail2ban or similar intrusion prevention systems to monitor and block suspicious authentication patterns. Network-level controls including IP address restrictions and connection throttling can provide additional defense in depth. The implementation of multi-factor authentication policies that enforce strong password requirements and account lockout mechanisms should be enforced across all administrative interfaces. Regular security audits and monitoring of authentication logs should be conducted to detect potential brute-force attempts. Organizations should also consider implementing security information and event management systems to correlate authentication failures and identify potential attack patterns. Compliance with industry standards such as NIST SP 800-53 and ISO 27001 requires proper authentication controls and monitoring capabilities that address vulnerabilities like CVE-2020-29136 through comprehensive security frameworks.