CVE-2022-4036 - Appointment Hour Booking Plugin for WordPress Vulnerable to CAPTCHA Bypass

A Critical Vulnerability (CVE-2022-4036) has been identified in the Appointment Hour Booking plugin for WordPress, affecting versions up to and including 1.3.72. This vulnerability allows an attacker to successfully bypass the CAPTCHA feature by exploiting an insufficiently strong hashing algorithm and accessing the CAPTCHA secret through cookies.

Details of the Vulnerability

The Appointment Hour Booking plugin is designed to help website administrators create and manage appointment booking forms for various services. One of the essential security features of this plugin is the implementation of CAPTCHA to prevent automated submissions and spam. However, the latest discovery of this vulnerability makes it possible for bad actors to bypass the CAPTCHA and perform malicious activities.

The root of the problem is a weak hashing algorithm used for hashing the CAPTCHA secret. This weakness allows an attacker to easily break the algorithm, access the CAPTCHA secret, and bypass the plugin's security feature. Additionally, the plugin stores the CAPTCHA secret in a cookie that is visible to the user, making it more susceptible to unauthorized access.

Code snippet

The vulnerable piece of code in the Appointment Hour Booking plugin is found within the dex_appointment_get_captcha function:

function dex_appointment_get_captcha($text)
{
   return strtoupper(md5($text)); // insufficiently strong hashing algorithm
}

It's important to note that the md5() function is used to hash the CAPTCHA secret, which is an outdated and weak hashing algorithm, making it easier for attackers to exploit this vulnerability.

For more information about this vulnerability, you can check the following resources

1. Official CVE details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-4036

2. Appointment Hour Booking Plugin Official Website: https://wordpress.org/plugins/appointment-hour-booking/

3. Plugin version history, confirming the issue exists in versions <= 1.3.72: https://wordpress.org/plugins/appointment-hour-booking/#developers

Prevention Measures

To prevent this vulnerability from being exploited on your WordPress site, it's crucial to take the following steps:

1. Ensure that all plugins, including Appointment Hour Booking, are updated to their latest available versions.

Consider using alternative CAPTCHA services with stronger security measures and robust algorithms.

3. Regularly review your site's security settings and disable any unnecessary cookies being sent to users.
4. Use trusted security plugins and implement proper access control mechanisms to protect your site from unauthorized access and malicious activities.

Conclusion

The discovery of the CVE-2022-4036 vulnerability highlights the importance of strong hashing algorithms and secure storage of sensitive information like CAPTCHA secrets. By taking the necessary precautions and updating your Appointment Hour Booking plugin, you can reduce the risk of this vulnerability being exploited on your WordPress site. Always stay vigilant and prioritize your site's security to protect your valuable data and reputation.

Timeline

Published on: 11/29/2022 21:15:00 UTC
Last modified on: 07/10/2023 18:45:00 UTC