On Thu, 17 Nov 2011 11:51:09 EST, "Larry W. Cashdollar" said:
> 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?
See above. :) (Seriously, that's a good one-para summary analysis of the
issue, better than a lot of 3rd-party advisories we see...)
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