CVE-2009-2335 in WordPress
Summary
by MITRE
WordPress and WordPress MU before 2.8.1 exhibit different behavior for a failed login attempt depending on whether the user account exists, which allows remote attackers to enumerate valid usernames. NOTE: the vendor reportedly disputes the significance of this issue, indicating that the behavior exists for "user convenience."
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Analysis
by VulDB Data Team • 12/03/2024
This vulnerability in WordPress and WordPress MU versions prior to 2.8.1 represents a classic timing-based username enumeration flaw that exposes the underlying authentication system to reconnaissance attacks. The issue stems from the inconsistent response behavior during failed login attempts, where the system provides different feedback depending on whether the attempted username exists in the database. This differential response creates a predictable pattern that malicious actors can exploit to determine valid usernames without requiring any privileged access or advanced techniques.
The technical implementation of this vulnerability occurs at the authentication layer where the WordPress core handles login failures. When an attacker attempts to log in with a non-existent username, the system typically performs additional database queries or processing that differs from the behavior when attempting to log in with an existing username. This difference manifests in varying response times or error messages that can be measured and analyzed. The vulnerability aligns with CWE-203, which specifically addresses "Information Exposure Through Discrepancy in Response," and represents a form of timing attack that can be automated through simple scripts or tools.
The operational impact of this vulnerability extends beyond simple username enumeration, as it provides attackers with a foundational element for subsequent attack phases. Once valid usernames are identified, attackers can proceed with brute force attacks, credential stuffing, or social engineering campaigns with significantly higher success rates. The vulnerability also enables account takeover attempts through targeted attacks against specific user accounts, particularly when combined with other information gathering techniques. According to ATT&CK framework, this represents a technique categorized under T1078.004 "Valid Accounts: Cloud Accounts" and T1586 "Compromise Account" where the initial enumeration phase directly enables more sophisticated attacks.
The vendor's response dismissing the issue as a "user convenience" aspect reveals a fundamental misunderstanding of security implications. This design decision, while potentially intended to improve user experience by providing more informative error messages, created a security weakness that directly violates the principle of least privilege and secure by default design. The inconsistency in authentication responses creates a side-channel attack vector that can be exploited by anyone with network access to the WordPress installation. Organizations running vulnerable versions face increased risk of account compromise, potential data breaches, and reputational damage from successful exploitation attempts.
Mitigation strategies for this vulnerability include upgrading to WordPress version 2.8.1 or later, where the authentication behavior was standardized to prevent username enumeration. Additional protective measures involve implementing rate limiting mechanisms, account lockout policies, and monitoring for suspicious login patterns. Network-level protections such as firewalls and intrusion detection systems can help detect and block automated enumeration attempts. Security teams should also consider implementing multi-factor authentication to add additional layers of protection beyond username and password authentication. The vulnerability demonstrates the importance of considering security implications during feature development and the need for comprehensive security testing that includes side-channel attack vectors.