Full Disclosure mailing list archives
Re: bind dos info?
From: Valdis.Kletnieks () vt edu
Date: Wed, 16 Nov 2011 21:13:45 -0500
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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Current thread:
- bind dos info? Larry W. Cashdollar (Nov 16)
- Re: bind dos info? Michael Wood (Nov 16)
- Re: bind dos info? Larry W. Cashdollar (Nov 16)
- Re: bind dos info? Michael Wood (Nov 16)
- Re: bind dos info? Larry W. Cashdollar (Nov 16)
- Re: bind dos info? Valdis . Kletnieks (Nov 16)
- Re: bind dos info? Jeffrey Walton (Nov 17)
- Re: bind dos info? Michael Wood (Nov 16)