Microsoft warns of virtual machine vulnerability

Microsoft warned users on Wednesday about two new security vulnerabilities affecting its Microsoft Virtual Machine, Microsoft Proxy Server 2.0 and Microsoft ISA Server 2000 products.

The Microsoft Virtual Machine (VM) contains a critical vulnerability that could allow a remote attacker to gain control of affected machines, according to security bulletin MS03-011. (See

The vulnerability, in code for a VM process called the ByteCode Verifier, could enable an attacker to use illegal sequences of byte codes to bypass security checks in the software, Microsoft said.

The ByteCode Verifier process is responsible for checking code as it is being loaded into the Virtual Machine, the company said.

Attackers could launch an attack using a Java applet embedded in a Web page or HTML (Hypertext Markup Language) format e-mail message. Once compromised, a vulnerable machine could be used to run the attacker's code, though only with the permission of the active user account, Microsoft said.

The Microsoft Virtual Machine is a key component of all supported versions of the Windows operating system, including Windows 2000 and Windows XP. It is also shipped with the Internet Explorer Web browser and other Microsoft software, the company said.

Despite being widespread, the new vulnerability is of only limited utility to attackers, Microsoft said.

Recent releases of the Outlook and Outlook Express e-mail clients as well as security patches for older versions prevent Java applets embedded in e-mail messages from being launched. Barring an e-mail borne attack, users would have to be tricked into visiting a Web page that contains the embedded Java applet containing the Virtual Machine attack.

Microsoft issued a patch for the virtual machine, build 3810, and recommended that customers who are using earlier builds upgrade.

Meanwhile, the Microsoft Proxy Server 2.0 and Microsoft ISA Server 2000 vulnerability could enable an individual on an internal network or the Internet to launch a denial of service (DOS) attack against those products, preventing them from responding to internal and external requests, according to information released in Microsoft security bulletin MS03-012. (

The vulnerability, which Microsoft rated "important," affects the Winsock Proxy service on Proxy Server 2.0 and the Firewall service on ISA Server 2000. Both services redirect communications from Internet applications to the machines running Proxy Server 2.0 or ISA Server, creating a path to the Internet through those products, according to Microsoft.

A flaw in the way each service handles inbound requests from remote clients means that attackers could use a specially formatted request to cause the products to stop responding.

Despite the denial of service capability, however, attackers could not gain remote access to either the ISA Server 2000 or Proxy Server 2.0 machines, Microsoft said.

Customers using the affected products were encouraged to download and install a patch that repairs the affected services, removing the DOS vulnerability.

Join the newsletter!

Error: Please check your email address.
Rocket to Success - Your 10 Tips for Smarter ERP System Selection
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Paul Roberts

IDG News Service
Show Comments



Victorinox Werks Professional Executive 17 Laptop Case

Learn more >

Sansai 6-Outlet Power Board + 4-Port USB Charging Station

Learn more >



Back To Business Guide

Click for more ›

Brand Post

Most Popular Reviews

Latest Articles


PCW Evaluation Team

Andrew Teoh

Brother MFC-L9570CDW Multifunction Printer

Touch screen visibility and operation was great and easy to navigate. Each menu and sub-menu was in an understandable order and category

Louise Coady

Brother MFC-L9570CDW Multifunction Printer

The printer was convenient, produced clear and vibrant images and was very easy to use

Edwina Hargreaves

WD My Cloud Home

I would recommend this device for families and small businesses who want one safe place to store all their important digital content and a way to easily share it with friends, family, business partners, or customers.

Walid Mikhael

Brother QL-820NWB Professional Label Printer

It’s easy to set up, it’s compact and quiet when printing and to top if off, the print quality is excellent. This is hands down the best printer I’ve used for printing labels.

Ben Ramsden

Sharp PN-40TC1 Huddle Board

Brainstorming, innovation, problem solving, and negotiation have all become much more productive and valuable if people can easily collaborate in real time with minimal friction.

Sarah Ieroianni

Brother QL-820NWB Professional Label Printer

The print quality also does not disappoint, it’s clear, bold, doesn’t smudge and the text is perfectly sized.

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?