CVE-2018-5734: A malformed request can trigger an assertion failure in badcache.c
  • 12 Nov 2018
  • 2 Minutes to read
  • Contributors
  • Dark
  • PDF

CVE-2018-5734: A malformed request can trigger an assertion failure in badcache.c

  • Dark
  • PDF

Article summary

CVE: CVE-2018-5734

Document version: 2.0

Posting date: 28 Feb 2018

Program impacted: BIND

Versions affected: 9.10.5-S1 to 9.10.5-S4, 9.10.6-S1, 9.10.6-S2

Severity: High

Exploitable: Remotely


While handling a particular type of malformed packet, BIND erroneously selects a SERVFAIL rcode instead of a FORMERR rcode. If the receiving view has the SERVFAIL cache feature enabled, this can trigger an assertion failure in badcache.c when the request doesn't contain all of the expected information.


Servers running the affected versions (9.10.5-S1 to 9.10.5-S4, 9.10.6-S1, and 9.10.6-S2) are vulnerable if they allow recursion, unless the SERVFAIL cache is disabled for the receiving view.

CVSS Score: 7.5


For more information on the Common Vulnerability Scoring System and to obtain your specific environmental score please visit:


Disabling the SERVFAIL cache with 'servfail-ttl 0;' will prevent taking the code path that leads to the assertion failure.

Active exploits: No known active exploits.

Solution: Upgrade to the patched release.

  • No publicly released versions of BIND are affected

BIND Supported Preview Edition is a special feature preview branch of BIND 9 provided to eligible ISC support customers.

  • BIND 9 version 9.10.6-S3

Document Revision History:
1.0 Advance Notification, 20 February 2018
2.0 Public Disclosure, 28 February 2018

Related Documents:

See our BIND 9 Security Vulnerability Matrix 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's PGP key which can be found here:  If you are unable to use encrypted email, you may also report new issues at:


ISC patches only currently supported versions. When possible we indicate EOL versions affected.  (For current information on which versions are actively supported, please see 

ISC Security Vulnerability Disclosure Policy:

Details of our current security advisory policy and practice can be found in the ISC Software Defect and Security Vulnerability Disclosure Policy.

This Knowledgebase article is the complete and official security advisory document.

Legal Disclaimer:

Internet Systems Consortium (ISC) is providing this notice on an "AS IS" basis. No warranty or guarantee of any kind is expressed in this notice and none should be implied. ISC expressly excludes and disclaims any warranties regarding this notice or materials referred to in this notice, including, without limitation, any implied warranty of merchantability, fitness for a particular purpose, absence of hidden defects, or of non-infringement. Your use or reliance on this notice or materials referred to in this notice is at your own risk. ISC may change this notice at any time.  A stand-alone copy or paraphrase of the text of this document that omits the document URL is an uncontrolled copy. Uncontrolled copies may lack important information, be out of date, or contain factual errors.