About CVE-2015-5477 ("An error in handling TKEY queries can cause named to exit with a REQUIRE assertion failure")

Ben Croswell ben.croswell at gmail.com
Tue Jul 28 23:06:16 UTC 2015

Is it safe to say the only vulnerable hosts would be those accepting
queries from the outside world, or would this also pertain servers getting
responses from the outside world with no inbound queries?
 On Jul 28, 2015 5:42 PM, "Michael McNally" <mcnally at isc.org> wrote:

> As the security incident manager for this particular vulnerability
> notification, I'd like to say a little extra, beyond our official
> vulnerability disclosure (https://kb.isc.org/article/AA-01272)
> about this critical defect in BIND.
> Many of our bugs are limited in scope or affect only users having
> a particular set of configuration choices.  CVE-2015-5477 does not
> fall into that category.  Almost all unpatched BIND servers are
> potentially vulnerable.  We know of no configuration workarounds.
> Screening the offending packets with firewalls is likely to be
> difficult or impossible unless those devices understand DNS at a
> protocol level and may be problematic even then.  And the fix for
> this defect is very localized to one specific area of the BIND code.
> The practical effect of this is that this bug is difficult to defend
> against (except by patching, which is completely effective) and will
> not be particularly difficult to reverse-engineer.  I have already
> been told by one expert that they have successfully reverse-engineered
> an attack kit from what has been divulged and from analyzing the code
> changes, and while I have complete confidence that the individual who
> told me this is not intending to use his kit in a malicious manner,
> there are others who will do so who may not be far behind.
> Please take steps to patch immediately.  This bug is designated
> "Critical" and it deserves that designation.
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