CVE-2019-16220 in WordPress
Summary
by MITRE
In WordPress before 5.2.3, validation and sanitization of a URL in wp_validate_redirect in wp-includes/pluggable.php could lead to an open redirect.
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Analysis
by VulDB Data Team • 08/21/2024
The vulnerability identified as CVE-2019-16220 represents a critical security flaw in WordPress versions prior to 5.2.3, specifically within the wp_validate_redirect function located in wp-includes/pluggable.php. This issue stems from inadequate input validation and sanitization of URLs, creating a potential vector for open redirect attacks that could be exploited by malicious actors to deceive users into visiting unintended destinations. The flaw exists in the core WordPress framework's redirection mechanism, which is fundamental to how the platform handles user navigation and authentication flows.
The technical implementation of this vulnerability resides in the wp_validate_redirect function's insufficient handling of URL parameters, particularly when processing redirects following user authentication or other navigation events. The function fails to properly validate and sanitize input URLs, allowing specially crafted malicious URLs to bypass security checks and potentially redirect users to phishing sites or other malicious destinations. This weakness operates at the application layer and can be exploited through various attack vectors including login pages, password reset flows, and other user interaction points where redirects are utilized. The vulnerability is classified as a CWE-601 Open Redirect vulnerability, which is categorized under the broader category of injection flaws that can be leveraged for social engineering attacks.
The operational impact of CVE-2019-16220 extends beyond simple redirection capabilities, as it can be weaponized in sophisticated phishing campaigns and man-in-the-middle attacks. Attackers can manipulate the redirect parameter to point to malicious domains, potentially stealing user credentials or installing malware through deceptive redirects that appear legitimate to end users. This vulnerability particularly affects WordPress installations that rely heavily on user authentication flows and external redirects, making it a significant concern for websites handling sensitive user data or those that are frequently targeted by cybercriminals. The attack surface is broad since redirect functionality is used throughout WordPress core operations, including login redirects, comment moderation, and various plugin integrations that may utilize redirect mechanisms.
Organizations and WordPress administrators should immediately update to version 5.2.3 or later to remediate this vulnerability, as the patch includes enhanced URL validation and sanitization routines that properly address the input handling issues. Additional mitigations include implementing proper web application firewalls, monitoring redirect parameters for suspicious patterns, and conducting regular security audits of WordPress installations. The vulnerability also highlights the importance of following the principle of least privilege in web application development and emphasizes the need for comprehensive input validation at all levels of application code. From an ATT&CK framework perspective, this vulnerability maps to T1566 Initial Access through Phishing and T1071.004 Application Layer Protocol DNS, as attackers can leverage the redirect functionality to establish malicious domains for credential theft. Organizations should also consider implementing Content Security Policy headers and other defensive measures to reduce the overall risk surface when dealing with redirect functionality in web applications.