Microsoft warns of critical Windows flaw

IDG News Service - Microsoft Corp. warned of a critical security flaw today that affects all supported versions of its Windows operating system and could enable a remote attacker to run malicious code on unpatched Windows systems.
The security hole is due to a buffer-overrun vulnerability in the Windows HTML converter, a component that enables Windows to convert files from Rich Text Format (RTF) to HTML, which is used to display documents on the Web.
The flaw exists in an HTML converter feature used to handle content that's cut and pasted within Windows. When properly exploited, the flaw could cause the converter to crash, enabling an attacker to deposit and run his own code on the affected system, Microsoft said.
Because the converter is also used by the Internet Explorer Web browser, malicious hackers could launch attacks by sending specially crafted e-mail messages to vulnerable systems or tricking users into visiting Web pages designed to exploit the vulnerability.
Once a user visited such a site or opened an e-mail, no further user interaction would be required to cause the buffer overrun, Microsoft said.
Although the vulnerability was rated critical for most versions of the Windows operating system, the company noted that an attacker who successfully exploited the vulnerability would gain only the privilege level of the current user. For nonadministrative users, that could limit the damage caused on exploited systems.
Microsoft's Security Bulletin MS03-023 includes links to patches for all affected systems up to and including the most recent Windows Server 2003 release.
Microsoft encouraged all affected customers to apply the appropriate patch at the earliest possible opportunity.
In addition to the HTML converter vulnerability, Microsoft issued patches for two other software flaws today, MS03-024 and MS03-025, both rated "important" by the company.
Bulletin MS03-024 concerns a buffer-overrun problem affecting the Server Message Block protocol on machines running Windows NT 4.0, 2000 and XP Professional. That problem, if left unpatched, could lead to the corruption of data stored on the system and allow an attacker to execute malicious code.
Bulletin MS03-025 concerns a flaw in Windows Utility Manager on systems running Windows 2000.
Utility Manager is used to monitor the status of some of Microsoft's accessibility options for persons with disabilities. The vulnerability could enable a malicious user to perform actions on the system in excess of his privilege level.