Q815021 vs Q811493:

Unchecked Buffer in Windows
Component May Cause
Web Server Compromise

vs

Buffer Overrun in Windows
Kernel Message Handling
Could Lead to Elevated Privileges

There seems to be allot of confusion over these TWO security patches released by Microsoft... So this article should explain things regarding Q815021 and Q811493.

For the FULL scoop on Q811493 visit www.updatexp.com/q811493.html 

So What's The Story With Q811493 ?

On the 16th April 2003. Microsoft released Windows XP Security Patch Q811493 as a Critical update via the Microsoft Windows Update website.

This patch was designed to fix a vulnerability in Windows XP and Windows 2000 where an attacker could gain access of a users machine.

However this patch had a problem in the way it "updated" some XP SP1 machines and therefore caused many performance issues. Microsoft subsequently downgraded the Windows XP Security Patch Q811493 a few days later from Critical to Recommended.

On the 28th May 2003 Microsoft released a "Revised"  Windows XP Security Patch Q811493, and upgraded it to Critical again.

This new Windows XP Security Patch Q811493 seems to be working OK.

So What's The Story With Q815021 ?

On the 17th March 2003. Microsoft released Windows XP Security Patch Q815021 as a Critical update via the Microsoft Windows Update website.

This patch was designed to fix a vulnerability in Windows XP and Windows 2000 where an attacker could run code on the users machine in certain circumstances.

However this patch caused many performance issues for users of Windows 2000 SP2 who had applied Hot fixes between December 2001 and February 2002. The Q815021 was incompatible with these 12 Hot fixes and caused lots of "Stop Errors" on rebooting Windows 2000 SP2. (more commonly known as Blue Screens.)

On the 28th May 2003 Microsoft released a "Revised"  Critical Windows Security Patch Q815023.

This new Windows Security Patch Q815021 seems to be working OK.

Conclusion

The two patches Q815021 and Q811493 are different patches addressing different security concerns with Microsoft's software. The ONLY similarity is that they were BOTH released to the general public in a "Revised" form on 28th May 2003.

I hope this article helps clarify things!

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This page was last updated 8th July 2003