CVE-2023-6520 in WP 2FA Plugin
Summary
by MITRE • 01/11/2024
The WP 2FA – Two-factor authentication for WordPress plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 2.5.0. This is due to missing or incorrect nonce validation on the send_backup_codes_email function. This makes it possible for unauthenticated attackers to send emails with arbitrary content to registered users via a forged request granted they can trick a site administrator or other registered user into performing an action such as clicking on a link. While a nonce check is present, it is only executed if a nonce is set. By omitting a nonce from the request, the check can be bypassed.
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Analysis
by VulDB Data Team • 04/11/2026
The vulnerability identified as CVE-2023-6520 affects the WP 2FA – Two-factor authentication for WordPress plugin, a widely used security extension for wordpress platforms. This issue represents a critical cross-site request forgery weakness that undermines the plugin's ability to protect user accounts through proper authentication mechanisms. The vulnerability exists in all versions up to and including 2.5.0, making it a persistent threat across multiple releases of the plugin. The flaw specifically targets the send_backup_codes_email function which serves as a critical component for backup authentication methods. This function is designed to send email notifications containing backup authentication codes to users who have enabled two-factor authentication, but the security implementation contains a fundamental flaw that allows malicious actors to exploit this functionality.
The technical implementation of this vulnerability stems from improper nonce validation within the plugin's codebase. A nonce is a cryptographic value that serves as a time-based token to verify the authenticity of requests and prevent unauthorized actions. In this case, the plugin implements a nonce check mechanism but fails to enforce it consistently. The validation logic only executes when a nonce is present in the request, creating a bypass opportunity for attackers. By simply omitting the nonce parameter from their malicious requests, attackers can circumvent the validation entirely. This design flaw directly violates security best practices and represents a classic example of inadequate input validation and authentication checks. The vulnerability operates under the CWE-352 category, which specifically addresses Cross-Site Request Forgery issues in software applications. The weakness allows attackers to perform unauthorized actions within the context of a logged-in user's session, potentially compromising user accounts and undermining the entire two-factor authentication system.
The operational impact of this vulnerability extends beyond simple email spamming, as it can be leveraged to execute more sophisticated attacks against WordPress site administrators and registered users. An attacker can craft malicious requests that appear legitimate to the WordPress system, tricking administrators into unknowingly sending backup code emails to users with arbitrary content. This capability can be used to distribute phishing content, spread malware through email attachments, or manipulate user authentication states. The attack vector requires social engineering to convince target users to click on malicious links or visit compromised websites, but once executed, it can result in unauthorized access to user accounts, data breaches, and potential privilege escalation. The vulnerability affects the core security model of the two-factor authentication system, essentially rendering the backup code functionality ineffective as a security control. This weakness can be exploited by attackers with minimal technical skill and no authentication credentials, making it particularly dangerous in environments where administrators may be targeted through spear-phishing campaigns.
Mitigation strategies for CVE-2023-6520 should focus on immediate plugin updates to versions that address the nonce validation flaw. Users should also implement additional security measures such as monitoring email traffic for unusual backup code deliveries and educating administrators about recognizing social engineering attempts. Network-level protections including web application firewalls and email filtering systems can help detect and block malicious requests targeting this vulnerability. The ATT&CK framework categorizes this vulnerability under T1566, which covers Phishing techniques, as the attack relies heavily on tricking users into performing malicious actions. Organizations should also consider implementing multi-factor authentication controls beyond just the plugin's backup codes and establish regular security audits of installed WordPress plugins. The vulnerability highlights the importance of proper nonce implementation and the necessity of defensive programming practices that do not rely on optional security checks. Regular vulnerability scanning and security assessments of WordPress installations are essential to identify and remediate similar issues that could compromise user authentication systems.