CVE-2018-5741 Explained : Impact and Mitigation

BIND 9 offers a feature called update-policy to allow precise control over the use of Dynamic DNS (DDNS) in updating records within a zone. However, the documentation inaccurately described the behavior of two rule types, krb5-subdomain and ms-subdomain, potentially misleading operators. This affects versions of BIND prior to 9.11.5 and 9.12.3.

Understanding CVE-2018-5741

This CVE addresses the incorrect documentation of update-policy behavior in BIND 9, specifically related to krb5-subdomain and ms-subdomain rule types.

What is CVE-2018-5741?

CVE-2018-5741 highlights the discrepancy between the intended behavior of krb5-subdomain and ms-subdomain update policy rule types and their inaccurate documentation in BIND 9 versions prior to 9.11.5 and 9.12.3.

The Impact of CVE-2018-5741

The inaccurate documentation could mislead operators into believing their configured policies were more restrictive than they actually were, potentially leading to unintended security vulnerabilities.

Technical Details of CVE-2018-5741

This section delves into the vulnerability description, affected systems and versions, and the exploitation mechanism.

Vulnerability Description

The incorrect documentation of krb5-subdomain and ms-subdomain rules in BIND 9 could mislead operators into believing their update policies were more restrictive than they actually were, potentially leading to unintended security vulnerabilities.

Affected Systems and Versions

Product: BIND 9
Vendor: ISC
Versions Affected: BIND 9 Versions prior to BIND 9.11.5 and BIND 9.12.3

Exploitation Mechanism

The vulnerability arises from the discrepancy between the intended behavior of krb5-subdomain and ms-subdomain rules and their inaccurate documentation, potentially allowing unauthorized updates within a zone.

Mitigation and Prevention

This section outlines immediate steps to take, long-term security practices, and the importance of patching and updates.

Immediate Steps to Take

Review and update the update-policy configurations in BIND 9 to ensure they align with the intended restrictions.
Monitor for any unauthorized updates within zones.

Long-Term Security Practices

Regularly review and update BIND 9 configurations to align with security best practices.
Conduct periodic security audits to identify and address any misconfigurations or vulnerabilities.

Patching and Updates

Maintenance releases of BIND issued during or after October 2018 (9.11.5 or higher, 9.12.3 or higher) address the configuration bug and introduce new rule types, krb5-selfsub and ms-selfsub, to accurately implement the intended behavior of krb5-subdomain and ms-subdomain rules.