The security flaws rated "critical" - Microsoft's highest threat level - affect the company's Windows computer operating system, Internet Explorer browser, MSN Messenger, Microsoft Word software and Exchange server system.
"News of critical flaws in Microsoft Windows is becoming a regular occurrence," says CBS News Technology Analyst Larry Magid. "Still, it's important not to become complacent. Failure to download the latest software fix could leave you vulnerable to an attack that could jeopardize your security."
"These flaws," says Magid, "could lead to a hacker taking complete remote control over a user's computer."
Microsoft also released three other patches to fix Windows flaws that carry less of a security threat. But the company said those "important" bulletins also could allow a malicious user to take control of another person's computer.
All the flaws affect computers with operating systems dating back to Windows 98. Users who have installed Microsoft's massive security update for Windows XP, Service Pack 2, also will need to install some patches.