Internet Explorer is a set of core technologies in Microsoft Windows
operating systems that provide web browsing functionality. Further
information is available at:
Remote exploitation of an input validation error in Microsoft Corp.'s
Internet Explorer may allow the execution of arbitrary code.
The vulnerability specifically exists in the handling of long hostnames.
When IE is requested to open a URL with a hostname part longer than
about 256 characters, the heap becomes slightly corrupted. This
corruption may cause no visible effect, or it may cause the Address Bar
to contain a URL with "garbage" characters as the hostname. It may also
cause IE to crash, referencing an invalid memory address. In testing
done, the addresses referred during a crash are at times controllable by
the web page containing the malformed URL.
Successful exploitation allows remote attackers to execute arbitrary
code under the privileges of the current user.
Although it is not trivial to exploit this vulnerability, it is believed
to be possible. Testing during verification of this vulnerability
revealed multiple situations where remotely supplied values were used to
reference memory locations. A remote attacker may be able to read data
from, write data to, or execute arbitrary code by supplying
specifically malformed content.
iDEFENSE Labs has confirmed that Internet Explorer 6.0.2180 on Windows
XP with Service Pack 2 is vulnerable.
iDEFENSE is currently unaware of any effective workarounds for this
issue. The vulnerable functionality is a major part of the affected
product, and is it is not possible to disable it.
Although it will not prevent all means of exploitation, disable active
scripting if it is not necessary for day-to-day operations using the
1. In IE, click on Tools and select Internet Options from the
2. Click the Security tab and the Custom Level button.
3. Under Scripting, then Active Scripting, click the Disable radio
This vulnerability is addressed in Microsoft Security Bulletin MS05-020
The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2005-0554 to these issues. This is a candidate for inclusion
in the CVE list (http://cve.mitre.org), which standardizes names for
11/11/2004 Initial vendor notification
11/11/2004 Initial vendor response
04/12/2005 Coordinated public disclosure
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