full-disclosure - Re: bind dos info?

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Message-ID: <CAKKN48wVY2+Bf0+qbSfAe5PMf7ayxJLyO8X49XLMZ0+ymsWJHQ@mail.gmail.com>
Date: Wed, 16 Nov 2011 20:55:20 -0500
From: Michael Wood <itnetsec@...il.com>
To: "Larry W. Cashdollar" <bugs@....dhs.org>
Cc: full-disclosure@...ts.grok.org.uk
Subject: Re: bind dos info?

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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Full-Disclosure - We believe in it.
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