Re: bind dos info?

["Larry W. Cashdollar" <bugs () fbi dhs org>]

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 () fbi 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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