CVE-2015-8000: Responses with a malformed class attribute can trigger an assertion failure in db.c

AA-01317


Document Version:          
2.0
Posting date: 
15 December 2015
Program Impacted: 
BIND
Versions affected: 
9.0.x -> 9.9.8, 9.10.0 -> 9.10.3
Severity: 
Critical
Exploitable: 
Remotely

Description:

An error in the parsing of incoming responses allows some records with an incorrect class to be accepted by BIND instead of being rejected as malformed.  This can trigger a REQUIRE assertion failure when those records are subsequently cached. Intentional exploitation of this condition is possible and could be used as a denial-of-service vector against servers performing recursive queries.

Impact:

An attacker who can cause a server to request a record with a malformed class attribute can use this bug to trigger a REQUIRE assertion in db.c, causing named to exit and denying service to clients.  The risk to recursive servers is high. Authoritative servers are at limited risk if they perform authentication when making recursive queries to resolve addresses for servers listed in NS RRSETs.

CVSS Score:  7.1

CVSS Vector:  (AV:N/AC:M/Au:N/C:N/I:N/A:C)

For more information on the Common Vulnerability Scoring System and to obtain your specific environmental score please visit: https://nvd.nist.gov/cvss.cfm?calculator&version=2&vector=(AV:N/AC:M/Au:N/C:N/I:N/A:C)

Workarounds:

None. 

Active exploits:

No known active exploits.

Solution:  Upgrade to the patched release most closely related to your current version of BIND. Public open-source branches can be downloaded from http://www.isc.org/downloads.

  • BIND 9 version 9.9.8-P2
  • BIND 9 version 9.10.3-P2

BIND 9 Supported Preview edition is a feature preview version of BIND provided exclusively to ISC Support customers.

  • BIND 9 version 9.9.8-S3

Document Revision History:

1.0 Advance Notification, 24 November, 2015
1.1 Software releases 9.9.8-P1 and 9.10.3-P1 replaced with 9.9.8-P2 and 9.10.3-P2 to address CVE-2015-8461, advisory text and schedule updated, 8 December 2015
2.0 Public Disclosure, 15 December 2015
2.1 Edited to correct minor error in Description (repeated word), 15 December 2015

Related Documents:

See our BIND9 Security Vulnerability Matrix at https://kb.isc.org/article/AA-00913 for a complete listing of Security Vulnerabilities and versions affected.

Do you still have questions? 

Questions regarding this advisory should go to security-officer@isc.orgTo report a new issue, please encrypt your message using security-officer@isc.org's PGP key which can be found here: https://www.isc.org/downloads/software-support-policy/openpgp-key/.  If you are unable to use encrypted email, you may also report new issues at: https://www.isc.org/community/report-bug/.

Note: ISC patches only currently supported versions. When possible we indicate EOL versions affected.  (For current information on which versions are actively supported, please see http://www.isc.org/downloads/). 

ISC Security Vulnerability Disclosure Policy:  Details of our current security advisory policy and practice can be found here: https://kb.isc.org/article/AA-00861/164/ISC-Software-Defect-and-Security-Vulnerability-Disclosure-Policy.html

This Knowledge Base article https://kb.isc.org/article/AA-01317 is the complete and official security advisory document.

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