Microsoft Patches JVM Flaws

One of the flaws gives an attacker complete control of a user's machine.

Microsoft Corp. on Wednesday released a patch to fix three flaws in its Java Virtual Machine, one of which gives an attacker complete control of a users machine.

The release comes 10 days after news of the vulnerabilities was posted to a security mailing list. The BugTraq posting discusses more than 10 flaws although the new patch from Microsoft fixes just three of them.

The Microsoft VM shipped with most versions of Windows, including Windows 95, 98 and 98 SE, Me, NT 4.0 Service Pack 1 and later, 2000 and XP Service Pack 1. It also ships as part of most Internet Explorer versions.

All of the new vulnerabilities could be exploited by an attacker creating a Web page with hostile code and enticing a user to view the page, Microsoft said in its advisory.

The most serious of the new vulnerabilities lies in a Java class that provides support for the use of XML by Java applications. The class exposes several native methods, some of which are only designed for use by trusted applets and others that can be used by any applet. This Java class does not differentiate between the kinds of applets, meaning that an applet could take essentially any action on a users system that an attacker wanted.

The other two flaws both involve the Java database Connectivity classes, which allow Java applications to use data from a variety of sources, including SQL Server databases. One of the vulnerabilities enables an attacker to spoof a request to load a DLL on a users system. The attacker could thereby load and run any DLL.

The second flaw results because the JDBC classes fail to correctly validate handles provided as input. One result of an exploit of the flaw would be that Internet Explorer would crash. Microsoft officials said there is a theoretical attack that could allow an attacker to run code in the security context of the user, as well.

The patch for these flaws is available here.

The Redmond, Wash., company also released a patch for two flaws in the Remote Data Protocol used by Terminal Services in Windows NT 4.0 and 2000 and by the Remote Desktop service in Windows XP. The problems affect the cryptographic process used to encrypt data sent during an RDP session.

The checksums for the plaintext session data are sent in the clear, which means anyone who could eavesdrop on the RDP session could take that data and use it to decrypt the session traffic.

Also, the Remote Desktop implementation in Windows XP fails when it receives certain malformed packets. This failure in turn causes the operating system itself to crash.

The patch for these problems is available here.

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