http://www.microsoft.com/technet/security/bulletin/MS02-019.asp

Unchecked Buffer in Internet Explorer and Office for Mac Can Cause Code to Execute (Q321309)

Originally posted: April 16, 2002

Summary

Who should read this bulletin: All users of Microsoft® Internet Explorer and Office for the Macintosh®

Impact of vulnerability: Run code of attacker's choice.

Maximum Severity Rating: Critical

Recommendation: Customers running Internet Explorer and Office for Macintosh should apply the patches.

Affected Software:
- Microsoft Internet Explorer 5.1 for Macintosh OS X
- Microsoft Internet Explorer 5.1 for Macintosh OS 8 & 9
- Microsoft Outlook Express 5.0.-5.0.3 for Macintosh
- Microsoft Entourage v. X for Macintosh
- Microsoft Entourage 2001 for Macintosh
- Microsoft PowerPoint v. X for Macintosh
- Microsoft PowerPoint 2001 for Macintosh
- Microsoft PowerPoint 98 for Macintosh
- Microsoft Excel v. X for Macintosh
- Microsoft Excel 2001 for Macintosh

Technical description:

This is a cumulative patch that, when applied, eliminates all previously released security vulnerabilities affecting IE 5.1 for Macintosh, and Office v. X for Macintosh.In addition, it eliminates two newly discovered vulnerabilities.
- The first is a buffer overrun vulnerability associated with the handling of a particular HTML element. Because of support for HTML in Office applications, this flaw affects both IE and Office for Macintosh. A security vulnerability results because an attacker can levy a buffer overrun attack against IE that attempts to exploit this flaw. A successful attack would have the result of causing the program to fail, or to cause code of the attacker's choice to run as if it were the user.
- The second is a vulnerability that can allow local AppleScripts to be invoked by a web page. This vulnerability can allow locally stored AppleScripts to be invoked automatically without first calling the Helper application. The AppleScripts would run as if they had been launched by the user, and could take the same actions as any AppleScript legitimately launched by the user. The AppleScript would have to already be present on the system; there is no way for an attacker to deliver an AppleScript of her choosing through this vulnerability.

Mitigating factors:

Unchecked Buffer in HTML Element:
- Successfully exploiting this issue with Office files requires that a user accept files from an unknown or untrusted source. Users should never accept files unknown or untrusted sources. Accepting files only from trusted sources can prevent attempts to exploit this issue.
- A successful attack using HTML email would require specific knowledge of the user's mail client and cannot be mounted against PC users.
- A successful attack using an HTML web page would require the attacker to lure the user to visiting a site under her control. Users who exercise caution in their browsing habits can potentially protect themselves from attempts to exploit this vulnerability.
- On operating systems that enforce security on per-user basis, such as Mac OS X, the specific actions that an attacker's code can take would be limited to those allowed by the privileges of the user's account.

Local AppleScript Invocation:
- The vulnerability only affects IE on Mac OS 8 & 9.
- A successful attack requires that the attacker know the full path and file name of any AppleScript they want to invoke.
- The vulnerability provides no means to deliver an AppleScript of the attacker's construction: it can only invoke AppleScripts already present on the user's system.

Vulnerability identifier:
- Unchecked Buffer in HTML Element:CAN-2002-0152
- Local AppleScript Invocation:CAN-2002-0153

This email is sent to NTBugtraq automatically as a service to my subscribers. Since its programmatically created, and since its been a long time since anyone paid actual money for my programming skills, it may or may not look that good...;-]

I can only hope that the information it does contain can be read well enough to serve its purpose.

Cheers,
Russ - Surgeon General of TruSecure Corporation/NTBugtraq Editor

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