Microsoft plans to fix critical bugs in its Word, Publisher and Jet database software next week.

The software vendor also plans to release a less-critical update for its anti-virus products, fixing a flaw that attackers could use to launch a denial of service (DoS) attack against products such as Windows Live OneCare and Microsoft Forefront Security.

The updates will be released Tuesday, the day set aside for Microsoft's monthly set of security patches. Microsoft has provided some early details on the patches.

Microsoft considers flaws to be critical when they could be exploited by attackers in order to run unauthorised software on a victim's system.

Although Microsoft's note does not describe the bugs in detail, it looks like the company is planning to fix a known bug in the Jet database engine, which was disclosed in late March. Attackers had figured out a new way to launch a malicious Jet file using Microsoft Word, Microsoft warned in a blog posting.

Jet files, which have a .mdb extension, are typically blocked by Outlook, but "attackers have figured out a way to work around the mitigations built into Outlook," Microsoft said in its post.

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The Jet flaw affects Windows XP, 2000 and Server 2003 Service Pack 1.

The Word flaw is rated critical for both Windows and Mac users.

Although rated only "moderate," the DoS bug in Microsoft's security products is also a cause for concern. It affects many Microsoft security products including OneCare, Antigen, Windows Defender, Standalone System Sweeper and several Forefront Security products.