Microsoft Security Bulletin (MS98-008)
Long Filename Attachment Vulnerability affecting Microsoft (R) Outlook (TM)98 and Microsoft Outlook Express 4.x
Last Revision: August 11, 1998
Recently Microsoft was notified by AUSCERT (http://www.auscert.org.au), OUSPG (http://www.oulu.fi/Welcome.html) and NTBugtraq (http://ntbugtraq.ntadvice.com) of a security vulnerability affecting the way Microsoft email clients handle file attachments with extremely long filenames.
On July 27th Microsoft published patches for Outlook 98 and Outlook Express 4.x that fixed the vulnerability reported to us by OUSPG. As part of our on-going security review process and analysis, we discovered a variant of the original vulnerability, and on August 11th, we posted updated versions of the patches that addresses all known vulnerabilities.
Microsoft strongly recommends that all users download the appropriate updated patch to be protected against these vulnerabilities. Note: Customers should obtain these patches by downloading them from the Web sites listed below, or through some other trusted mechanism, such as through their ISP. While Microsoft has been sending email notifications to their customers to alert them to this issue and the availability of a patch, Microsoft does not send the patches in the email. Customers who receive an email with an attachment that claims to be a patch, should not install it.
The purpose of this bulletin is to inform Microsoft customers of this issue, its applicability to Microsoft products, and the availability of countermeasures Microsoft has developed to further secure its customers.
When the email client receives a malicious mail or news message that contains an attachment with a very long filename, it could cause the email client to shut down unexpectedly. These very long filenames do not normally occur in mail or news messages, and must be intentionally created by someone with malicious intent. A skilled hacker could use this malicious email message to run arbitrary computer code contained in the long string.
This issue can cause one of the following to occur when attempting to download, open or view an mail or news message in Microsoft Outlook 98 or Microsoft Outlook Express 4.x that has an attachment with a very long filename.
An error message similar to the following may be displayed:
Outlook 98 or Outlook Express may terminate unexpectedly.
When Outlook 98 attempts to download a mail or news message with a file attachment that has a filename greater than a certain length, Outlook could terminate unexpectedly. The user does not have to open the message or attachment in order for this to occur.
This issue affects all users of Outlook 98.
Outlook 97 is not affected by this issue.
When the user attempts to open an attachment in Outlook Express mail or news client and the attachment has a filename longer than a certain number of characters, the client could terminate unexpectedly.
Outlook Express 4.01 for Microsoft Windows 3.1 and Windows NT 3.51 are not affected by this issue.
On July 27th Microsoft published patches for Outlook 98 and Outlook Express 4.x that fixed the vulnerability reported to us by OUSPG. This vulnerability was caused by improper handling of file attachments with very long filenames in Outlook 98 and Outlook Express 4.x.
As part of our on-going security review process and analysis, we discovered a variant of the original vulnerability. On August 11th, we posted updated versions of the patches originally posted on July 27th, which fixes all known vulnerabilities.
Microsoft has sent this security bulletin (MS98-008)
to the Microsoft Product Security Notification Service.
In addition, Microsoft has notified CERT, an industry security organization, which distributes information to corporate, government and end-users.
Microsoft highly recommends that customers download and apply the appropriate updates listed below. Note: Customers should obtain these patches by downloading them from the Web sites listed below, or through some other trusted mechanism, such as through their ISP. While Microsoft has been sending email notifications to their customers to alert them to this issue and the availability of a patch, Microsoft does not send the patches in the email. Customers who receive an email with an attachment that claims to be a patch should not install it.
Customers using Microsoft Outlook 98 for Windows 95, Windows 98 or Windows NT 4.0 should download the updated Outlook 98 patch from Office Update at http://www.microsoft.com/outlook/enhancements/outptch2.asp
Localized versions of the Outlook 98 patch will be released shortly.
Customers using Outlook Express 4.0 that comes with Internet Explorer 4.0 on Windows 95, Windows 98 or Windows NT 4.0 must first upgrade to Internet Explorer 4.01 SP1 (http://www.microsoft.com/ie/download), then install the Outlook Express updated patch listed below.
Customers using Microsoft Outlook Express 4.01 or 4.01 SP1 for Windows 95, Windows 98, Windows NT 4.0 or the Macintosh should download the available updated patch from the Internet Explorer security Web site, http://www.microsoft.com/ie/security/oelong.htm
Windows 98 customers can also get the updated Outlook Express patch using the Windows Update feature of Windows 98. For more information, please visit the Windows Update site, http://windowsupdate.microsoft.com
The patch for Microsoft Outlook Express 4.01 for Solaris will be released shortly. When this patch is available, it will be announced at http://www.microsoft.com/security
Localized versions of the Outlook Express 4.x patch will be released shortly.
Please see the following references for more information related to this issue.
For additional security-related information about Microsoft products, please visit http://www.microsoft.com/security
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