PT-2012-27: Privilege Gaining in UMI.CMS

Vulnerable software

UMI.CMS
Version: 2.8.5.2 and earlier

Application link:
http://www.umi-cms.ru/

Severity level

Severity level: High
Impact: Administrator Privilege Gaining
Access Vector: Remote  

CVSS v2:
Base Score: 10
Vector: (AV:N/AC:L/Au:N/C:C/I:C/A:C)

CVE: not assigned

Software description

UMI.CMS is a system that allows users to manage sites.

Vulnerability description

Positive Research Center experts detected a vulnerability that exists as confirmation code (that is used to reset passwords for all accounts including administrator account) and new generated passwords are predictable.

Vulnerable code: classes/modules/users/__forget.php

$avLetters = "$#@^&!1234567890qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM";
$size = strlen($avLetters);
$npass = "";
for($i = 0; $i < $length; $i++) {
$c = rand(0, $size - 1);
$npass .= $avLetters[$c];
}

You need to know user login if you want to reset its password. An attacker can easily check if the login exists, if he tries to register with the login (error-login-exists error class). It is possible because UMI.CMS gets random numbers via PHP function rand, and does not initialize the random number generator via srand function called with  SEED parameter. In this case, PHP automatically calls srand function with predictable SEED based on session number that allows attackers to predict every further result of rand function call. Also in Windows this code provides only 2^15 possible values of generated tokens.

How to fix

Update your software up to the latest version.

Advisory status

16.08.2012 - Vendor is notified
17.08.2012 - Vendor gets vulnerability details
20.11.2012 - Vendor releases fixed version and details
11.02.2013 - Public disclosure

Credits

The vulnerabilities has discovered by Timur Yunusov, Positive Research Center (Positive Technologies Company)

References

http://en.securitylab.ru/lab/PT-2012-27

Reports on the vulnerabilities previously discovered by Positive Research:

http://ptsecurity.com/research/advisory/
http://en.securitylab.ru/lab/

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