April shower of Microsoft vulnerabilities ends in May

April showers brought May flowers, at least that appears to be the story from Microsoft on the issue of software security vulnerabilities.

One month after it disclosed dozens of software vulnerabilities, then watched as malicious code and a new family of worms appeared to exploit those holes, Microsoft decided to take it easy in May, publishing just one bulletin Tuesday covering a single noncritical vulnerability in some versions of Windows.

The company released a software patch and a security bulletin, MS04-015, describing a vulnerability in the Windows Help and Support Center (HSC). A problem with the way the HSC handles information in URLs (uniform resource locators) could allow a remote attacker to run malicious code on vulnerable Windows machines, potentially giving them total control over compromised systems, Microsoft said.

HSC URLs, which use the Host Configuration Protocol (HCP) and begin with “hcp://,” link to help resources in Windows and are similar to Web URLs, which use HTTP and begin with “http://.”

To take advantage of the hole, an attacker would have to trick Windows users into clicking on an HSC link that was embedded in a Web page or an e-mail message formatted in HTML. Once clicked, the attacker could open a Help window containing content of the attacker’s choosing. However, the user would still need to interact with the attacker’s Help page and perform other actions to complete the attack, Microsoft said.

Microsoft issued updates for the 32- and 64-bit editions of Windows XP and Windows XP Service Pack 1, as well as 32- and 64-bit editions of Windows Server 2003. Windows NT, 2000 and 98 are not affected by the HSC vulnerability, Microsoft said.

The low-key security warning stands in marked contrast to April, when Microsoft published four security bulletins, MS04-011, 012, 013 and 014. Those bulletins contained patches for 20 unique software vulnerabilities, including critical holes in Microsoft’s Secure Sockets Layer library and the Local Security Authority Subsystem Service (LSASS), which is used to authenticate users locally and also in client-server environments.

Malicious code to exploit those holes appeared within days of publication of the bulletins and a new worm, Sasser, was released on May 1 that exploited the LSASS hole and already may have infected over a million Windows machines worldwide.

Microsoft encouraged customers to install the May update at their earliest opportunity, but cautioned that doing so would disable some Windows features.

Citing its “defense in depth” strategy of securing its products, Microsoft said MS04-015 patch removes a Windows XP feature that enabled Windows to automatically offer users the option of upgrading a DVD device driver because the feature exposed users to unspecified “malicious use.” Installing the May patch will also break a feature in the Windows “Found New Hardware Wizard” that transmitted hardware profile information after the wizard runs.

Customers who install the patch will receive error messages when try to use those features, Microsoft said.