CVE-2016-3167 in Drupal
Summary
by MITRE
Open redirect vulnerability in the drupal_goto function in Drupal 6.x before 6.38, when used with PHP before 5.4.7, allows remote attackers to redirect users to arbitrary web sites and conduct phishing attacks via a double-encoded URL in the "destination" parameter.
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Analysis
by VulDB Data Team • 10/05/2018
The CVE-2016-3167 vulnerability represents a critical open redirect flaw within the Drupal content management system that specifically affects version 6.x prior to 6.38. This vulnerability exploits a weakness in the drupal_goto function's handling of URL redirection parameters, creating a significant security risk for Drupal 6 installations running on PHP versions earlier than 5.4.7. The flaw enables malicious actors to manipulate the destination parameter through double-encoded URLs, effectively bypassing standard security mechanisms designed to prevent unauthorized redirections. The vulnerability operates at the application layer and demonstrates how improper input validation can lead to severe consequences in web application security.
The technical root cause of this vulnerability stems from the inadequate sanitization of URL parameters within the drupal_goto function implementation. When PHP versions before 5.4.7 process double-encoded URLs, the application fails to properly decode and validate the destination parameter, allowing attackers to inject malicious URLs that will be processed as legitimate redirects. This behavior creates a pathway for attackers to construct phishing pages that appear to originate from trusted Drupal domains, exploiting the trust relationship between users and the application. The vulnerability specifically leverages the interaction between PHP's URL decoding behavior and Drupal's redirection logic, where the double encoding bypasses the expected validation checks. This type of flaw aligns with CWE-601 Open Redirect vulnerability classification, which specifically addresses situations where applications redirect users to unvalidated external URLs.
The operational impact of CVE-2016-3167 extends beyond simple redirection attacks to enable sophisticated social engineering campaigns that can compromise user credentials and sensitive information. Attackers can craft malicious URLs that redirect users to phishing sites designed to capture login credentials or personal data, making this vulnerability particularly dangerous for organizations relying on Drupal 6 for their web presence. The vulnerability affects any Drupal 6 installation that has not been updated to version 6.38 or later, and particularly impacts systems running PHP versions below 5.4.7 where the underlying PHP decoding behavior creates the exploitable condition. Organizations using this vulnerable configuration face significant risk of user compromise, brand damage, and potential data breaches through these phishing attacks. The vulnerability also represents a persistent threat vector that can be exploited repeatedly until the underlying software is patched or updated.
Mitigation strategies for CVE-2016-3167 require immediate action to update Drupal installations to version 6.38 or later, which includes the necessary patches to properly validate and sanitize URL redirection parameters. Organizations should also consider upgrading their PHP runtime environment to version 5.4.7 or higher to eliminate the underlying PHP behavior that enables the exploitation. Network-level protections such as URL filtering and content inspection systems can provide additional defense in depth, though these measures are secondary to proper application patching. Security monitoring should include detection of suspicious redirection patterns and unusual destination parameter usage within Drupal applications. Organizations should also implement proper input validation and sanitization practices throughout their web applications, following secure coding guidelines that prevent similar vulnerabilities from occurring in other components. The vulnerability demonstrates the importance of keeping web applications updated and highlights the risks associated with running deprecated software versions in production environments. This issue relates to ATT&CK technique T1566.001 Phishing, where the open redirect serves as a delivery mechanism for malicious content, and T1071.004 Application Layer Protocol: Web Protocols, as it exploits web application redirection mechanisms to achieve its malicious objectives.