------------------------------------------------------------------------
Concrete5 <= 8.5.5 (Logging Settings) Phar Deserialization Vulnerability
------------------------------------------------------------------------


[-] Software Link:

https://www.concrete5.org


[-] Affected Versions:

Version 8.5.5 and prior versions.


[-] Vulnerability Description:

The vulnerable code is located within the 
/concrete/controllers/single_page/dashboard/system/environment/logging.php 
script. Specifically, into the Logging::update_logging()  method:

61.      public function update_logging()
62.      {
63.          $config = $this->app->make('config');
64.          $request = $this->request;
65.
66.          if (!$this->token->validate('update_logging')) {
67.              return 
$this->showError($this->token->getErrorMessage());
68.          }
69.
70.          // Load in variables from the request
71.          $mode = (string) $request->request->get('logging_mode') === 
'advanced' ? 'advanced' : 'simple';
72.          $handler = $mode === 'simple' ? (string) 
$request->request->get('handler', 'database') : null;
73.          $logFile = $handler === 'file' ? (string) 
$request->request->get('logFile') : null;
74.          $enableDashboardReport = 
$request->request->get('enable_dashboard_report') ? true : false;
75.          $loggingLevel = strtoupper((string) 
$request->request->get('logging_level'));
76.          $intLogErrorsPost = 
$request->request->get('ENABLE_LOG_ERRORS') === 1 ? 1 : 0;
77.          $intLogEmailsPost = 
$request->request->get('ENABLE_LOG_EMAILS') === 1 ? 1 : 0;
78.          $intLogApiPost = $request->request->get('ENABLE_LOG_API') 
=== 1 ? 1 : 0;
79.
80.
81.          // Handle 'file' based logging
82.          if ($handler === 'file') {
83.              $directory = dirname($logFile);
84.
85.              // Validate the file name
86.              if (pathinfo($logFile, PATHINFO_EXTENSION) !== 'log') {
87.                  return $this->showError(t('The filename provided 
must be a valid filename and end with .log'));
88.              }
89.
90.              // Validate the file path, create the log file if needed
91.              if (!file_exists($logFile)) {


User input passed through the "logFile" request parameter is not 
properly sanitized before being used in a call to the file_exists() 
function at line 91. This can be exploited by malicious users to inject 
arbitrary PHP objects into the application scope (PHP Object Injection 
via phar:// stream wrapper), allowing them to carry out a variety of 
attacks, such as executing arbitrary PHP code. Successful exploitation 
of this vulnerability requires an administrator account.


[-] Solution:

No official solution is currently available.


[-] Disclosure Timeline:

[20/12/2020] - Vendor notified through HackerOne
[22/12/2020] - Vendor asks suggestions to fix the issue, feedback 
provided
[18/03/2021] - Version 8.5.5 released, vulnerability not fixed
[02/06/2021] - Asked for an update, no response
[06/07/2021] - Asked for an update, no response
[16/07/2021] - CVE number assigned
[19/07/2021] - Public disclosure


[-] CVE Reference:

The Common Vulnerabilities and Exposures project (cve.mitre.org)
has assigned the name CVE-2021-36766 to this vulnerability.


[-] Credits:

Vulnerability discovered by Egidio Romano.


[-] Other References:

https://hackerone.com/reports/1063039


[-] Original Advisory:

http://karmainsecurity.com/KIS-2021-05