CVE-2011-3126 in WordPress
Summary
by MITRE
WordPress 3.1 before 3.1.3 and 3.2 before Beta 2 allows remote attackers to determine usernames of non-authors via canonical redirects.
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Analysis
by VulDB Data Team • 11/17/2021
WordPress version 3.1 before 3.1.3 and 3.2 before Beta 2 contained a vulnerability that exposed user authentication information through improper handling of canonical redirects. This flaw allowed remote attackers to enumerate usernames of individuals who lacked author privileges within the system. The vulnerability specifically manifested when the application processed requests that triggered canonical redirect behavior, enabling attackers to distinguish between valid and invalid usernames through response differences. The technical implementation involved the application's failure to properly sanitize or normalize URL parameters during redirect operations, creating a side-channel information disclosure mechanism. This weakness falls under the category of information disclosure vulnerabilities and aligns with CWE-200, which addresses the improper exposure of sensitive information. The impact of this vulnerability extends beyond simple username enumeration as it provides attackers with intelligence for targeted social engineering campaigns or brute force attacks against user accounts. The vulnerability operates at the application layer and can be classified under ATT&CK technique T1087.001 for account discovery. Attackers could exploit this by sending crafted requests to the WordPress installation and observing the different redirect responses for valid versus invalid usernames. The canonical redirect functionality in WordPress was designed to ensure proper URL handling and prevent duplicate content issues, but the implementation failed to consider the security implications of exposing user account existence. This vulnerability represents a classic case of insufficient input validation where the application's redirect logic did not adequately protect against information leakage. The flaw demonstrates how seemingly benign application features can become security risks when proper access control and information hiding principles are not applied. Security researchers identified that the vulnerability could be exploited through simple HTTP request manipulation without requiring authentication or special privileges. The affected versions of WordPress were widely deployed across the web, making this vulnerability particularly dangerous as it provided attackers with a method to gather user intelligence for subsequent attacks. The canonical redirect mechanism in WordPress typically handles URL normalization by redirecting users to the proper canonical URL for a given resource. However, in this instance, the implementation allowed the application to respond differently to requests for non-existent usernames compared to requests for existing usernames, thereby revealing which accounts were valid within the system. The vulnerability was classified as a medium severity issue but presented significant risk due to its ability to facilitate further attacks. Organizations running vulnerable WordPress installations were advised to upgrade immediately to versions 3.1.3 or 3.2 Beta 2 where the issue was resolved through improved redirect handling and input validation. The fix implemented by WordPress developers involved modifying the canonical redirect logic to ensure consistent responses regardless of whether the requested username existed, thereby eliminating the information disclosure channel. This vulnerability highlights the importance of proper security testing during application development, particularly for features that handle user input and generate responses based on account existence. The issue also demonstrates how security considerations must be integrated throughout the software development lifecycle rather than treated as an afterthought. The canonical redirect functionality, while useful for search engine optimization and proper URL handling, required additional security controls to prevent information leakage. This vulnerability serves as a reminder that even standard web application features can introduce security risks when not properly implemented with security in mind. The impact on affected organizations included potential exposure of user account lists that could be used for targeted attacks, social engineering, or credential stuffing attacks against other systems. The vulnerability was particularly concerning because it could be exploited by anyone with access to the web application, requiring no special privileges or authentication. Modern security practices would classify this as a design flaw in the application's response handling that violated fundamental security principles of least privilege and information hiding. The resolution of this vulnerability required changes to the core WordPress codebase, specifically in how the application handles URL canonicalization for user-related requests. This incident underscored the importance of security reviews for all application functionality, particularly features that interact with user data and generate different responses based on data existence. The vulnerability also demonstrated the need for comprehensive testing that includes security considerations during the development and deployment phases of web applications.