CVE-2018-5745: An assertion failure can occur if a trust anchor rolls over to an unsupported key algorithm when using managed-keys
  • Updated on 21 Feb 2019
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CVE-2018-5745: An assertion failure can occur if a trust anchor rolls over to an unsupported key algorithm when using managed-keys

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CVE: CVE-2018-5745

Document version: 2.0

Posting date: 21 February 2019

Program impacted: BIND

Versions affected: BIND 9.9.0 -> 9.10.8-P1, 9.11.0 -> 9.11.5-P1, 9.12.0 -> 9.12.3-P1, and versions 9.9.3-S1 -> 9.11.5-S3 of BIND 9 Supported Preview Edition. Versions 9.13.0 -> 9.13.6 of the 9.13 development branch are also affected. Versions prior to BIND 9.9.0 have not been evaluated for vulnerability to CVE-2018-5745.

Severity: Medium

Exploitable: Remotely.

Description:

"managed-keys" is a feature which allows a BIND resolver to automatically maintain the keys used by trust anchors which operators configure for use in DNSSEC validation. Due to an error in the managed-keys feature it is possible for a BIND server which uses managed-keys to exit due to an assertion failure if, during key rollover, a trust anchor's keys are replaced with keys which use an unsupported algorithm.

Impact:

This particular vulnerability would be very difficult for an arbitrary attacker to use because it requires an operator to have BIND configured to use a trust anchor managed by the attacker. However, if successfully exercised, the defect will cause named to deliberately exit after encountering an assertion failure.

It is more likely, perhaps, that this bug could be encountered accidentally, as not all versions of BIND support the same set of cryptographic algorithms. Specifically, recent branches of BIND have begun deliberately removing support for cryptographic algorithms that are now deprecated (for example because they are no longer considered sufficiently secure.) This vulnerability could be encountered if a resolver running a version of BIND which has removed support for deprecated algorithms is configured to use a trust anchor which elects to change algorithm types to one of those deprecated algorithms.

  • Support for GOST was removed from BIND in 9.13.1.
  • Support for DSA was removed from BIND in 9.13.4
  • Support for RSAMD5 will be removed from future BIND releases in the 9.13 branch and higher.

CVSS Score: 4.9

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

Workarounds:

None.

Active exploits:

None known.

Solution:

Upgrade to a version of BIND containing a fix preventing the assertion failure.

  • BIND 9.11.5-P4
  • BIND 9.12.3-P4

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

  • BIND 9.11.5-S5

Document revision history:

1.0 Advance Notification, 23 January 2019
2.0 Public Disclosure, 21 February 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.

Legal Disclaimer:

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