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                   Defcom Labs Advisory def-2001-02



              IBM Websphere 3.52 Kernel Leak DoS



Author: Peter Gründl 

Release Date: 2001-01-08

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------------------------=[Brief Description]=-------------------------

The Apfa cache in the IBM HTTP Server, which Websphere is built on,

has problems handling certain types of URL requests. The result of

such a URL is a kernel leak, which will eventually end up consuming

all available kernel memory and rendering the host useless.



------------------------=[Affected Systems]=--------------------------

- IBM WebSphere 3.52 (IBM HTTP Server 1.3.12) for Windows NT



----------------------=[Detailed Description]=------------------------

Sending a continous stream of HTTP requests resulting in "bad request"

will cause a kernel leak in Windows NT. There are many ways to trigger

the bad request result that triggers the leak,



eg. GET / HTTP/1.0\r\nuser-agent: 20000xnull\r\n\r\n



---------------------------=[Workaround]=-----------------------------

Comment out the three lines beginning with "Apfa" in the httpd.conf

file (located in the conf directory in the web server folder).



-------------------------=[Vendor Response]=--------------------------

This issue was brought to the vendor's attention on the 8th of

December, 2000. A workaround was received from the vendor on the 5th

of January, 2001.



"This issue is caused by a problem in the AfpaCache module of the IBM

HTTP Server. The only workaround at this time is to disable the

AfpaCache. IBM Development is working on fixing this issue, but it is

not yet known when a fix will be available."



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