CVE-2018-5741 in BIND
Summary
by MITRE
To provide fine-grained controls over the ability to use Dynamic DNS (DDNS) to update records in a zone, BIND 9 provides a feature called update-policy. Various rules can be configured to limit the types of updates that can be performed by a client, depending on the key used when sending the update request. Unfortunately, some rule types were not initially documented, and when documentation for them was added to the Administrator Reference Manual (ARM) in change #3112, the language that was added to the ARM at that time incorrectly described the behavior of two rule types, krb5-subdomain and ms-subdomain. This incorrect documentation could mislead operators into believing that policies they had configured were more restrictive than they actually were. This affects BIND versions prior to BIND 9.11.5 and BIND 9.12.3.
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Analysis
by VulDB Data Team • 07/01/2023
The vulnerability described in CVE-2018-5741 affects the Berkeley Internet Name Domain (BIND) software version 9.11.5 and 9.12.3, specifically targeting the Dynamic DNS update-policy feature that controls zone record modifications. This issue stems from incorrect documentation in the Administrator Reference Manual (ARM) that was introduced during change #3112, where the behavior of two rule types krb5-subdomain and ms-subdomain was inaccurately described. The flaw creates a potential security risk through configuration misinterpretation, as administrators might believe their security policies are more restrictive than they actually are, leading to unintended access to DNS zone updates that should be limited.
The technical implementation of this vulnerability lies in the update-policy configuration mechanism within BIND that allows administrators to define specific rules for DNS zone updates based on authentication keys. When operators configure policies using the krb5-subdomain and ms-subdomain rule types, they rely on documentation that incorrectly describes how these rules function. This misconfiguration can result in overly permissive access controls where clients may perform DNS updates that should be restricted, potentially allowing unauthorized modifications to DNS records in zone files. The vulnerability specifically affects the administrative configuration process rather than core BIND functionality, making it a configuration management issue that can have significant security implications.
The operational impact of this vulnerability extends beyond simple misconfiguration as it creates a false sense of security for DNS administrators who may believe their update policies are properly restricting access to zone records. When administrators implement policies based on the incorrect documentation, they inadvertently create more permissive environments where malicious actors or unauthorized users could potentially perform DNS zone updates that should be restricted. This could lead to DNS cache poisoning attacks, unauthorized domain modifications, or other malicious activities that compromise the integrity and availability of DNS services. The vulnerability affects both BIND 9.11.5 and 9.12.3 versions, indicating it was present across multiple release lines of the software.
The security implications of this vulnerability align with CWE-269, which addresses improper privilege management, and can be mapped to ATT&CK technique T1071.004 for application layer protocol usage in DNS operations. Organizations using BIND software must carefully review their DNS update-policy configurations, particularly those utilizing krb5-subdomain and ms-subdomain rule types, to ensure that their security policies are correctly implemented. The recommended mitigation involves updating to BIND versions 9.11.5 or 9.12.3 where the documentation has been corrected, and conducting thorough audits of existing DNS update policies to identify and remediate any misconfigurations that may have been introduced due to the incorrect documentation. Administrators should also implement additional monitoring and logging of DNS update activities to detect any unauthorized modifications that may occur due to the misconfigured policies.
This vulnerability demonstrates the critical importance of accurate documentation in security software and highlights the potential risks associated with configuration management in DNS infrastructure. The issue underscores the need for thorough testing and validation of security policies, particularly when dealing with complex access control mechanisms that govern critical network services. Organizations should treat this vulnerability as a reminder to regularly validate their security configurations and ensure that documentation and implementation align properly to maintain the intended security posture of their DNS infrastructure.