Software Engineering Institute

A vulnerability exists in the way Microsoft Excel handles malformed records.

Per Microsoft Security Bulletin MS07-002:
A remote code execution vulnerability exists in Microsoft Excel. An attacker could exploit this vulnerability when Excel parses a file and processes a malformed record.

A remote unauthenticated attacker may be able to execute arbitrary code on a vulnerable system.

Upgrade

Microsoft has issued an update to address this issue. See Microsoft Security Bulletin MS07-002 for more details.

Note that Microsoft has re-released the updates in Microsoft Security Bulletin MS07-002 for Excel 2000. See the Microsoft Security Response Center blog for more information.

Do not open untrusted Excel documents

Do not open unfamiliar or unexpected Excel or other Office documents, particularly those hosted on web sites or delivered as email attachments. Please see Cyber Security Tip ST04-010.

Do not rely on file name extension filtering

In most cases, Windows will call Excel to open a document even if the document has an unknown file extension. For example, if spreadsheet.qwer contains the correct file header information, Windows will open spreadsheet.qwer with Excel. Filtering for common extensions (e.g., .xls, .xlt, .csv) will not detect all Excel documents.