Microsoft yesterday issued a cumulative patch for Internet Explorer - the fixes to no less than six newly discovered vulnerabilities.
The software giant assigns the patch (for IE 5.01, 5.5 and 6.0) as 'critical' and lists a series of flaws the most serious of which could enable an attacker to execute commands on a user's system. The patch is the latest of a series of cumulative patches issued by Microsoft, which has so far manifestly failed to shore up the numerous flaws in its browser software. We hope this one does a better job, but we're not particularly optimistic.
This time around we have a fix for a buffer overrun vulnerability affecting an ActiveX control used to display specially formatted text, which could be exploited by an attacker to run code on a victim's PC, and another buffer overflow vulnerability affecting the Gopher protocol handler.
Next up there's a flaw which could enable an attacker to misrepresent the source of a file offered for download in an attempt to fool users into downloading files from untrusted sources believing it to be coming from a trusted source. Plenty of mischief to be had from that bug, then.
Then there's a vulnerability involving how Internet Explorer handles an HTML directive that displays XML data, which might allow the bad guys to read data from sites you'd previously visited once they were able to tempt victims to a maliciously constructed Web page
A Cross Domain verification vulnerability could enable a malicious Web site operator to read, but not change, any file on the user's local computer that could be viewed n a browser window. The bug arises because of improper domain checking in conjunction with the Object tag.
Finally there's a flaw which gives a fresh twist on cross-site scripting. Like the original vulnerability, this variant could enable an attacker to create a Web page that, when opened, would run in the 'Local Computer' zone, allowing it to run with fewer restrictions than it would in the 'Internet Zone'.
User are encouraged to review Microsoft's monster fix, which also includes the functionality of all previously released patches (we're told).
While you're mulling this you might want to consider less important security fixes.
Firstly there's a denial of service risk involving SMB (Server Message Block), the protocol Microsoft uses to share files, printers, serial ports, which arises because of a buffer overrun bug.
By sending a specially crafted packet request, an attacker can mount a denial of service attack on the target server machine and crash the system. It might also be possible to execute arbitrary code this way, Microsoft admits, though this aspect of the problem remains unconfirmed.
The bug affects Windows NT4, 200 server and workstation editions as well as Windows XP professional. Details of a patch, and possible workarounds, can be found in Microsoft's advisory. The advisory includes more than the usual share of mitigating arguments and suggested workarounds from Redmond, some of which won't work in file and print environments, which makes them of limited value.
Before we forget, there's also another patch designed to address a buffer overrun flaw in Microsoft Terminal Services Advanced Client (TSAC) ActiveX Control. This bug might be exploited to run code of an attackers choice through either getting users to open a maliciously constructed Web page or through a poisoned email message.
Because the TSAC Active X control does not come installed in Windows client system, instead coming from Web servers that offer terminal services, Microsoft describes the problem as only moderately severe. The servers themselves aren't affected by the bug, Microsoft reassures us in its advisory. ®