The vulnerabilities, first reported by a Chinese group and then posted to the Bugtraq mailing list, are in Windows' LoadImage API function, its animated cursor files, and in the way it handles help files. All of the bugs are as yet unpatched.
All currently-supported versions of Windows -- Windows NT, 2000, XP, and Windows Server 2003 -- are affected by the three flaws, said Venustech, the Chinese security firm that posted analysis on Bugtraq. Some impact Windows XP Service Pack 2 (SP2), some don't.
The LoadImage API vulnerability, for instance -- the latest in a series of image-related vulnerabilities that have hit Windows, Unix, and Linux -- affects Windows NT through Windows Server 2003. Whether Windows XP SP2 is at risk, however, isn't yet known.
This vulnerability could be exploited by attackers who entice users to a malicious Web site that includes a specially-crafted icon, cursor, animated cursor, or bitmap file, said Danish security firm Secunia in its alert. Alternately, the malicious image could be delivered via HTML e-mail. Users who view such messages or visit such sites could find their systems hijacked by hackers, who would be able to run their own code remotely on the PC.
The second bug, which is in Windows' ANI (animated cursor) files, could be used by an attacker to crash or freeze a Windows PC, said Venustech in its analysis. Windows XP SP2 is not vulnerable to this flaw, however.
But it is to the third, and last, of the trio, which revolves around how Windows parses help files. The bug can be exploited to create a buffer overflow, and thus give attackers control of the computer, if users open a maliciously-crafted help file posted on a site or sent to them via e-mail.
Secunia bundled the three bugs and labeled the group as a "highly critical" vulnerability, the second highest warning the firm uses. "Don't visit untrusted Web sites and don't open documents from untrusted sources," advised Secunia.
The SANS Institute's Internet Storm Center (ISC) gave similar stay-clear advice. "Try not to install help files until some Tuesday in, we hope, January," the center reported.
The ISC reference to Tuesday relates to Microsoft's practice of releasing patches on the second Tuesday of every month. The next scheduled security bulletin/patch day is Jan. 11, 2005.