CVE-2019-6471: A race condition when discarding malformed packets can cause BIND to exit with an assertion failure

CVE: CVE-2019-6471

Document version: 2.0

Posting date: 19 June 2019

Program impacted: BIND

Versions affected: BIND 9.11.0 -> 9.11.7, 9.12.0 -> 9.12.4-P1, 9.14.0 -> 9.14.2. Also all releases of the BIND 9.13 development branch and version 9.15.0 of the BIND 9.15 development branch. BIND Supported Preview Edition versions 9.11.3-S1 -> 9.11.7-S1.

Severity: Medium

Exploitable: Remotely

Description:

A race condition which may occur when discarding malformed packets can result in BIND exiting due to a REQUIRE assertion failure in dispatch.c.

Impact:

An attacker who can cause a resolver to perform queries which will be answered by a server which responds with deliberately malformed answers can cause named to exit, denying service to clients.

CVSS Score: 5.9

CVSS Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

For more information on the Common Vulnerability Scoring System and to obtain your specific environmental score please visit: https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

Workarounds:

None.

Active exploits:

None known.

Solution:

Upgrade to the patched release most closely related to your current version of BIND:

• BIND 9.11.8
• BIND 9.12.4-P2
• BIND 9.14.3
• BIND 9.15.1

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

• BIND 9.11.8-S1

Acknowledgements: ISC would like to thank CERN for helping us to discover this issue.

Document revision history:

1.0 Early Notification, 12 June 2019
2.0 Public Disclosure, 19 June 2019

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.org. To 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 https://www.isc.org/downloads/.)

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.

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