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How to remediate – WordPress 2.3.0 – 4.8.3 Unauthorized Password Reset

Contents

1. Introduction

The WordPress 2.3.0 – 4.8.3 Unauthorized Password Reset vulnerability is a security bypass affecting several versions of the popular content management system. It allows an unauthenticated attacker to attempt password resets for any user account. This could lead to complete compromise of website accounts and data, impacting confidentiality, integrity, and availability. Systems running WordPress between versions 2.3.0 and 4.8.3 are affected.

2. Technical Explanation

The vulnerability lies within the wp_mail() function in wp-includes/pluggable.php. Specifically, it’s caused by improper handling of the SERVER_NAME variable when processing password reset requests initiated via ‘wp-login.php?action=lostpassword’. An attacker can manipulate the HTTP Host header to control the SMTP server used for sending the reset key. This allows them to redirect the reset email to their own mailbox. Exploitation requires specific conditions, such as preventing the victim from receiving legitimate emails or relying on auto-replies. The vulnerability is identified as CVE-2017-8295.

  • Root cause: Improper usage of the SERVER_NAME variable in the wp_mail() function, allowing control via the HTTP Host header.
  • Exploit mechanism: An attacker crafts a malicious ‘wp-login.php?action=lostpassword’ request with a manipulated Host header to redirect the password reset email.
  • Scope: WordPress versions 2.3.0 through 4.8.3 are affected.

3. Detection and Assessment

Confirming vulnerability requires checking the installed WordPress version. A thorough assessment involves reviewing server configurations for potential Host header manipulation.

  • Quick checks: Check the WordPress version in the admin dashboard (Settings > General) or by viewing the source code of a public page.
  • Scanning: Nessus plugin ID 5a4aa4f1 can identify this vulnerability based on self-reported version number. Note that Nessus does not actively test for it.
  • Logs and evidence: Examine web server access logs for ‘wp-login.php?action=lostpassword’ requests with unusual Host headers.
wp --info

4. Solution / Remediation Steps

There is currently no official patch available from WordPress. Mitigation involves configuring the web server to enforce a static SERVER_NAME value.

4.1 Preparation

  • Changes should be made during a scheduled maintenance window with appropriate approval from IT management.

4.2 Implementation

  1. Step 1: Edit your Apache configuration file (e.g., httpd.conf or apache2.conf).
  2. Step 2: Enable the UseCanonicalName setting within the virtual host configuration for your WordPress site.
  3. Step 3: Restart the Apache web server to apply the changes.

4.3 Config or Code Example

Before

<VirtualHost *:80>
    ServerName yourdomain.com
    # UseCanonicalName is not set
</VirtualHost>

After

<VirtualHost *:80>
    ServerName yourdomain.com
    UseCanonicalName On
</VirtualHost>

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this type of vulnerability. Least privilege limits the impact of successful exploitation, while input validation blocks malicious data. Safe defaults reduce the attack surface and patch cadence ensures timely updates.

  • Practice 1: Implement least privilege for WordPress database users to limit potential damage from compromised accounts.
  • Practice 2: Regularly review and update WordPress core files, themes, and plugins to apply security patches promptly.

4.5 Automation (Optional)

Configuration management tools like Ansible can automate the enforcement of UseCanonicalName across multiple servers.

# Example Ansible task
- name: Enable UseCanonicalName in Apache configuration
  lineinfile:
    path: /etc/apache2/apache2.conf # Adjust path as needed
    regexp: '^UseCanonicalName'
    line: 'UseCanonicalName On'
  notify: Restart Apache

5. Verification / Validation

Confirm the fix by verifying that the UseCanonicalName setting is enabled and re-running a vulnerability scan. A smoke test should confirm basic website functionality remains intact.

  • Post-fix check: Check your Apache configuration file to ensure ‘UseCanonicalName On’ is present in the relevant virtual host section.
  • Re-test: Re-run the Nessus scan (plugin ID 5a4aa4f1) and confirm it no longer reports the vulnerability.
  • Smoke test: Verify that users can still log in to WordPress and access core website features, such as creating posts or pages.
grep 'UseCanonicalName On' /etc/apache2/apache2.conf

6. Preventive Measures and Monitoring

Update security baselines to include the requirement for UseCanonicalName in Apache configurations. Implement automated checks in CI/CD pipelines to prevent insecure configurations from being deployed. Maintain a regular patch review cycle for WordPress core, themes, and plugins.

  • Baselines: Update your server hardening baseline or CIS benchmark to require ‘UseCanonicalName On’ in Apache configuration files.
  • Asset and patch process: Implement a monthly review cycle for WordPress core, themes, and plugins to ensure timely application of security patches.

7. Risks, Side Effects, and Roll Back

Enabling UseCanonicalName may cause issues with virtual hosting configurations that rely on the Host header for routing requests. If this occurs, roll back by disabling UseCanonicalName in the Apache configuration file and restarting the server.

  • Roll back: Step 1: Edit your Apache configuration file (e.g., httpd.conf or apache2.conf). Step 2: Comment out or remove the ‘UseCanonicalName On’ line. Step 3: Restart the Apache web server to apply the changes.

8. References and Resources

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