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Microsoft Corp. on Tuesday issued patches for several severe security flaws in Windows, Internet Explorer, FrontPage Server Extensions and some Office applications, many of which allow for remote code execution.
Hardest hit in this months batch of patches is IE, which contains five newly discovered vulnerabilities. Three of the flaws are related to the cross-domain security model in the browser. This mechanism is meant to prevent windows in different domains from sharing information. However, these weaknesses allow an attacker to run script in the browsers My Computer zone, which typically does not carry the same level of security as the Internet zone might.
In order to exploit this flaw, the attacker would either need to entice the user into visiting a malicious Web site or opening an HTML mail message containing the attack code. This would let the attacker access data from other Web sites that the user has visited and read files on the users machine, Microsoft said in its bulletin.
Another flaw in IE concerns the manner in which the browser passes zone data to XML objects. Like the other three vulnerabilities, this one also can be exploited via Web sites and HTML mail messages. However, the attack also requires that users agree to download an HTML file, which would let the attacker read local files on the users machine, if he knows the exact location of the files.
The final weakness in IE affects drag-and-drop operations during dynamic HTML events. If a user clicked on a link supplied by an attacker, the attacker could save a file on a users machine in an arbitrary location. All of these flaws affect IE 5.01, 5.5 and 6, including IE 6, Service Pack 1.
The batch of patches also addresses a buffer overrun flaw in Windows 2000 and XP that could allow an attacker to run arbitrary code on remote machines. The vulnerability is in the Workstation service in Windows and a successful exploitation would give the attacker complete control of the compromised PC, Microsoft said.
Windows XP users who have installed the patch for MS03-043 are already protected against this vulnerability, but all Windows 2000 users would still need to apply this latest patch.
Microsoft also issued patches for security flaws in Word 97, 98, 2000 and 2002 and Excel 97, 2000 and 2002. The Excel issue relates to the way that the application checks spreadsheets before reading macros. An attacker could write a malicious macro and embed it in an Excel spreadsheet, which if opened by the user, would bypass the macro security settings and execute automatically. The macro would then be able to take any action on the users PC.
The weakness in Word results because the application incorrectly checks the length of macros embedded in Word documents. An attacker could exploit this by creating a malicious document that would overflow a data value in Word and execute arbitrary code.
There are also two new vulnerabilities in Microsofts FrontPage Server Extensions. The flaws affect 2000, 2002 and SharePoint Team Services 2002.
The first flaw is a buffer overrun in the remote debug function. An exploitation of this flaw would let an attacker run code with Local System privileges. The second vulnerability is a denial-of-service condition in the SmartHTML interpreter in FrontPage Server Extensions.
The patches are at Microsofts Security and Privacy Page.
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