The cybersecurity community has recently identified a significant vulnerability in phpServerMon, a popular open-source server monitoring software. The issue, classified as problematic, affects the function 'setUserLoggedIn' in the file 'src/psm/Service/User.php'. This vulnerability is known as CVE-2021-4241 and arises from the use of a predictable algorithm in the random number generator. An exploit has been disclosed to the public, increasing the risk of potential attacks. To mitigate this vulnerability, users should apply the recommended patch: bb10a5f3c68527c58073258cb12446782d223bc3. This vulnerability is also tracked under the identifier VDB-213744.

Code Snippet

The code snippet below demonstrates the vulnerable part of the 'setUserLoggedIn' function in the 'src/psm/Service/User.php' file:

public function setUserLoggedIn($user_id, $stayloggedin = false) {
      $random = rand();

As shown in the snippet above, the 'rand()' function is used, which introduces the vulnerability because it is predictable.

Exploit Details

The CVE-2021-4241 vulnerability directly affects the random number generation used for session management in phpServerMon. The exploitation of this vulnerability allows an attacker to predict session tokens easily, leading to unauthorized access and potential compromise of the monitored servers.

For more accurate and detailed information about the CVE-2021-4241 vulnerability, its mitigation, and the patch provided, please visit the links below:

1. CVE Details: A comprehensive database of vulnerability details, including descriptions, related vulnerabilities, and severity scores.
2. National Vulnerability Database(NVD): The U.S. government's repository of standards-based vulnerability management data, which includes technical details and mitigation recommendations.
3. phpServerMon GitHub Repository: The official GitHub repository for the phpServerMon project, including the patch bb10a5f3c68527c58073258cb12446782d223bc3 to fix the CVE-2021-4241 vulnerability.


CVE-2021-4241 is a critical vulnerability in phpServerMon, caused by the use of a predictable algorithm in the random number generator. It is important for users of phpServerMon to understand the risks posed by this vulnerability and take preemptive measures to ensure the security of their servers, starting by applying the patch bb10a5f3c68527c58073258cb12446782d223bc3.


Published on: 11/15/2022 23:15:00 UTC
Last modified on: 07/18/2023 13:52:00 UTC