[AusNOG] [ISC Security Advisory] BIND 9 Resolver crashes after logging an error in query.c

[Peter Losher]

BIND 9 Resolver crashes after logging an error in query.c

Summary: Organizations across the Internet reported crashes interrupting service on BIND 9 nameservers performing recursive queries. Affected servers crashed after logging an error in query.c with the following message: "INSIST(! dns_rdataset_isassociated(sigrdataset))" Multiple versions were reported being affected, including all currently supported release versions of ISC BIND 9. ISC is actively investigating the root cause and has produced patches which prevent the crash. Further information will be made available soon.

CVE: CVE-2011-4313
Document Version: 1.1
Document URL: http://www.isc.org/software/bind/advisories/cve-2011-4313 
Posting date: 16 Nov 2011
Program Impacted: BIND
Versions affected: All currently supported versions of BIND, 9.4-ESV, 9.6-ESV, 9.7.x, 9.8.x
Severity: Serious
Exploitable: Remotely

Description: 
An as-yet unidentified network event caused BIND 9 resolvers to cache an invalid record, subsequent queries for which could crash the resolvers with an assertion failure. ISC is working on determining the ultimate cause by which a record with this particular inconsistency is cached.At this time we are making available a patch which makes named recover gracefully from the inconsistency, preventing the abnormal exit. 

The patch has two components. When a client query is handled, the code which processes the response to the client has to ask the cache for the records for the name that is being queried. The first component of the patch prevents the cache from returning the inconsistent data. The second component prevents named from crashing if it detects that it has been given an inconsistent answer of this nature.

CVSS Score: 7.8

CVSS Equation: (AV:N/AC:L/Au:N/C:N/I:N/A:C) 

Workarounds: 
No workarounds are known. The solution is to upgrade. Upgrade BIND to one of the following patched versions: BIND 9.8.1-P1, 9.7.4-P1, 9.6-ESV-R5-P1, 9.4-ESV-R5-P1

Active exploits: 
Under investigation

Solution: 
Patches mitigating the issue are available at: 
https://www.isc.org/software/bind/981-p1
https://www.isc.org/software/bind/974-p1
https://www.isc.org/software/bind/96-esv-r5-p1
https://www.isc.org/software/bind/94-esv-r5-p1

ISC is receiving multiple reports and working with multiple customers on this issue. Please E-mail all questions, packet captures, and details to security-officer at isc.org

We very much appreciate all reports received on this issue.

Related Documents: 
Do you have Questions? Questions regarding this advisory should go to security-officer at isc.org.

ISC Security Vulnerability Disclosure Policy: Details of our current security advisory policy and practice can be found here: https://www.isc.org/security-vulnerability-disclosure-policy

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[ plosher at isc.org | Senior Operations Architect | ISC | PGP E8048D08 ]