full-disclosure - Re: bind dos info?

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Message-ID: <bdaf307153f6f4849bfe0b13f267dbb3.squirrel@fbi.dhs.org>
Date: Thu, 17 Nov 2011 12:04:30 -0500 (EST)
From: "Larry W. Cashdollar" <bugs@....dhs.org>
To: "Michael Wood" <itnetsec@...il.com>
Cc: full-disclosure@...ts.grok.org.uk
Subject: Re: bind dos info?

Thanks Michael!
 I guess 'ISC is working on determining the ultimate cause by which a
record with this particular inconsistency is cached' is the part I'm
interested in reading about and there are no details yet..

> http://www.isc.org/software/bind/advisories/cve-2011-4313
> On Nov 16, 2011 8:53 PM, "Larry W. Cashdollar" <bugs@....dhs.org> wrote:
>
>> Hello list,
>> I am wondering if anyone has more details on the bind9 DoS that just
>> came
>> out? (CVE-2011-4313) from what I can tell it appears a negative cached
>> DNS
>> object with a valid RR response associated with it(which shouldn't
>> exist)
>> will cause a vulnerabile bind9 server to crash.
>>
>> See lines 1890 - 1896 of query.c
>> 1890         if (result == DNS_R_NCACHENXRRSET) {
>> 1891                 dns_rdataset_disassociate(rdataset);
>> 1892                 /*
>> 1893                  * Negative cache entries don't have sigrdatasets.
>> 1894                  */
>> 1895                 INSIST(! dns_rdataset_isassociated(sigrdataset));
>> 1896         }
>>
>>
>> Since allowing recursive queries must be enabled for this to work the
>> attacker  must force a vulnerable dns server to query a malicous DNS
>> server by asking it to look up an NXrecord for a domain the attacker
>> controls dns for.  Sending a response of NXdomain but having actual DNS
>> results in the response.
>>
>> I am wondering if someone has seen a good write up out there?
>>
>> Thanks
>> -- Larry C$
>>
>>
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>

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Full-Disclosure - We believe in it.
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