Microsoft: Beware of Malformed Excel Files

Redmond's Patch Tuesday "critical" bulletin includes fixes for multiple code execution holes in the popular spreadsheet program.

Multiple security holes in Microsofts ubiquitous Excel spreadsheet program could put users at risk of PC takeover attacks, the software maker warned in a bulletin released March 14.

As part of its monthly batch of security updates, Microsoft pushed out patches for five code execution vulnerabilities in Excel and a separate bug in its Office desktop productivity suite that could allow an attacker to "take complete control" of a susceptible system.

The MS06-012 bulletin, which carries a "critical" rating, affects users of Office 2000, Office XP, Office 2003, Works Suites, Office X for Mac and Office 2004 for Mac.

Microsoft said the Excel flaws could be targeted by an attacker using a malformed range, a malformed parsing format file, a malformed description, a malformed graphic or a malformed record.

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The Microsoft Office vulnerability could be targeted by attacker using a specially crafted routing slip within an Office document. All the flaws require that the user be tricked into visiting a malicious Web site or opening a document.

Microsoft also released MS06-011, with a comprehensive fix for a privilege-elevation vulnerability first identified by a pair of Princeton University researchers.

The bulletin, which is rated "important," patches a hole that makes it easy for an attacker to pinpoint privilege escalation vulnerabilities in third-party applications running on Windows.

/zimages/6/28571.gifClick here to read about Microsofts pre-patch workarounds for the Windows privilege-escalation flaw.

The patch comes one month after the public release of proof-of-concept code that explained how ACLs (access control lists) used in Windows applications could be exploited.

The code can be used to exploit overly permissive access controls on third-party application services and could also be used to exploit default services of Windows XP Service Pack 1 and Windows Server 2003.

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An ACL is a table that tells a computer operating system which access rights each user has to a particular system object. But, because of poor software coding practices, the researchers found that some basic Windows security mechanisms can be bypassed and used in malicious hacker attacks.

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