CVE-2016-10769 in cPanel
Summary
by MITRE
cPanel before 60.0.25 allows an open redirect via /cgi-sys/FormMail-clone.cgi (SEC-162).
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Analysis
by VulDB Data Team • 07/20/2020
The vulnerability identified as CVE-2016-10769 represents a critical security flaw in cPanel versions prior to 60.0.25 that enables unauthorized open redirect attacks through the FormMail-clone.cgi script. This issue falls under the category of insecure redirect mechanisms and can be classified as CWE-601, which specifically addresses open redirect vulnerabilities where applications redirect users to external domains without proper validation. The vulnerability exists within the cgi-sys directory of cPanel installations, making it accessible through the standard web interface and potentially exploitable by malicious actors seeking to conduct phishing attacks or redirect users to malicious websites.
The technical implementation of this flaw occurs within the FormMail-clone.cgi script which processes form submissions and handles redirect parameters without adequate input sanitization or domain validation. When users submit forms through cPanel's mail functionality, the application accepts redirect URLs from user input without verifying that these URLs belong to the same domain or are otherwise authorized. This allows attackers to craft malicious URLs that appear to originate from legitimate cPanel domains while actually redirecting users to phishing sites or malicious content hosted on external domains. The vulnerability demonstrates a fundamental lack of proper access control and input validation mechanisms that should be implemented in all web applications handling user-supplied redirect parameters.
The operational impact of this vulnerability extends beyond simple redirection attacks and can result in significant security compromise for organizations using affected cPanel versions. Attackers can leverage this flaw to create convincing phishing campaigns that exploit the trusted cPanel domain to gain user credentials or install malware on victim systems. The open redirect vulnerability creates a trust exploitation vector where users are more likely to click on links that appear to come from legitimate administrative domains. This attack vector aligns with ATT&CK technique T1566, specifically targeting credential harvesting through social engineering and phishing methods. Organizations may experience reputation damage, data breaches, and potential regulatory compliance violations when such vulnerabilities are exploited in the wild.
Mitigation strategies for CVE-2016-10769 require immediate patching of affected cPanel installations to version 60.0.25 or later where the vulnerability has been resolved. System administrators should also implement additional defensive measures including monitoring for suspicious redirect patterns in web server logs and implementing web application firewalls that can detect and block malicious redirect attempts. Network-level controls such as domain-based access control lists and URL filtering can provide additional protection layers. Organizations should conduct thorough vulnerability assessments to identify all potentially affected systems and ensure that proper input validation is implemented throughout their web applications. The fix implemented in cPanel 60.0.25 includes enhanced parameter validation and domain checking mechanisms that prevent the exploitation of this particular vulnerability while maintaining legitimate redirect functionality for authorized use cases.