Information Disclosure and Insufficient Entropy in Zend Framework CAPTCHA Generation
Summary
GHSA-2fhr-8r8r-qp56: ZendFramework Information Disclosure and Insufficient Entropy vulnerability. Affects zendframework/zendframework versions >= 2.0.0, < 2.4.9. Fixed in 2.4.9. How to fix ↓
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Background
Zend Framework is a popular open-source framework for developing web applications and services in PHP. It provides a robust set of components for building secure and maintainable applications. One of its features includes CAPTCHA generation to prevent automated abuse of forms. However, the framework's CAPTCHA implementation has been found to use a random selection method that lacks sufficient entropy, making it vulnerable to brute-force attacks.
Vulnerability Detail
The vulnerability arises from the use of PHP's internal array_rand() function in the CAPTCHA generation process within Zend Framework. This function relies on rand(), which does not provide adequate randomness for cryptographic purposes. As a result, an attacker could potentially predict the generated CAPTCHA words, leading to information disclosure and the ability to bypass CAPTCHA protections. The vulnerability is classified under CWE-200 (Information Exposure) and CWE-331 (Insufficient Entropy).
How To Fix
Minimum fixed version
2.4.9
This is the first release that contains the fix.
composer require zendframework/zendframework:2.4.9Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, you can implement your own CAPTCHA generation logic that uses a more secure random number generation method, such as openssl_random_pseudo_bytes(). Here is a sample code snippet to generate a secure CAPTCHA word:
function generateSecureCaptchaWord($length = 6) {
$characters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
$charactersLength = strlen($characters);
$randomString = '';
for ($i = 0; $i < $length; $i++) {
$randomString .= $characters[ord(openssl_random_pseudo_bytes(1)) % $charactersLength];
}
return $randomString;
}
Conclusion
The Zend Framework vulnerability related to insufficient entropy in CAPTCHA generation poses a moderate risk of information disclosure. It is crucial for developers using this framework to update to the latest patched version to mitigate potential security threats. Utilizing tools like Vulert can help monitor and alert for such vulnerabilities in real-time.
See every vulnerability recorded for zendframework/zendframework →
FAQ
The vulnerability is related to insufficient entropy in the CAPTCHA generation process, making it susceptible to brute-force attacks.
You can check if your application is affected by using Vulert, which monitors open-source vulnerabilities in your software. Visit Vulert Scanner to analyze your composer.lock file.
If exploited, attackers could bypass CAPTCHA protections, leading to potential abuse of forms and unauthorized access to sensitive information.
Yes, the vulnerability has been patched in version 2.4.9 of Zend Framework. It is recommended to update to this version or later.
If immediate updating is not possible, consider implementing a custom CAPTCHA generation method using more secure random number generation techniques as a temporary workaround.
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