CVE-2012-5689 in BIND
Summary
by MITRE
ISC BIND 9.8.x through 9.8.4-P1 and 9.9.x through 9.9.2-P1, in certain configurations involving DNS64 with a Response Policy Zone that lacks an AAAA rewrite rule, allows remote attackers to cause a denial of service (assertion failure and named daemon exit) via a query for an AAAA record.
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Analysis
by VulDB Data Team • 05/04/2021
The vulnerability identified as CVE-2012-5689 affects ISC BIND versions 9.8.x through 9.8.4-P1 and 9.9.x through 9.9.2-P1, representing a critical denial of service flaw that specifically impacts DNS64 configurations. This vulnerability manifests when DNS64 is combined with Response Policy Zones that lack proper AAAA rewrite rules, creating a scenario where malicious actors can exploit the system's handling of AAAA record queries. The flaw results in assertion failures that cause the named daemon to terminate unexpectedly, effectively disrupting DNS services for all clients relying on the affected server. This issue falls under the CWE-119 category of "Improper Access of Resources" and represents a classic example of how complex DNS configurations can introduce unexpected failure points. The vulnerability is particularly concerning because it allows remote attackers to execute a denial of service attack without requiring authentication or specialized privileges, making it accessible to any network entity capable of sending DNS queries to the affected server.
The technical implementation of this vulnerability stems from the interaction between DNS64 functionality and Response Policy Zone processing within ISC BIND. When a DNS64 server receives a query for an AAAA record and the associated Response Policy Zone lacks a configured AAAA rewrite rule, the system fails to properly handle the assertion check that should validate the response. This assertion failure occurs during the processing of DNS responses where the server attempts to validate that the response contains appropriate AAAA records for the requested domain. The specific condition requires a particular configuration where DNS64 is enabled alongside Response Policy Zones that do not include AAAA rewrite rules, creating a path where the assertion logic encounters a scenario it cannot properly manage. This failure mode is consistent with the ATT&CK technique T1499.004 for "Endpoint Denial of Service" and demonstrates how DNS server implementations can fail to properly handle edge cases in their response processing logic. The assertion failure ultimately causes the named daemon to exit abruptly, leading to complete service disruption for all DNS resolution requests.
The operational impact of CVE-2012-5689 extends beyond simple service interruption, as it affects the fundamental reliability of DNS infrastructure that many organizations depend upon for their network operations. When the named daemon terminates due to this assertion failure, all DNS resolution services become unavailable until the process is manually restarted or the system automatically recovers through monitoring mechanisms. This vulnerability particularly affects organizations using DNS64 deployments for IPv6 transition, where the combination of DNS64 and Response Policy Zones creates the specific conditions necessary for exploitation. The attack vector requires only a remote DNS query for an AAAA record, making it extremely difficult to detect and prevent through traditional network monitoring. Organizations with DNS64 configurations that utilize Response Policy Zones without proper AAAA rewrite rules are at risk, and the vulnerability can be exploited by attackers from any location with network access to the affected DNS server. This flaw represents a significant concern for internet infrastructure providers and enterprise networks that rely on DNS64 for IPv6 transition strategies, as it can cause cascading failures in network services that depend on proper DNS resolution.
Mitigation strategies for CVE-2012-5689 should focus on both immediate patching and configuration hardening approaches. The primary recommendation is to upgrade to ISC BIND versions 9.8.4-P2 or 9.9.2-P2, which contain the necessary fixes to address the assertion failure in DNS64 Response Policy Zone processing. Organizations unable to immediately patch should implement configuration changes that ensure Response Policy Zones include proper AAAA rewrite rules for all domains that might be queried, preventing the specific conditions that trigger the assertion failure. Network administrators should also consider implementing monitoring solutions that can detect named daemon exits and automatically restart the service to minimize downtime. The vulnerability highlights the importance of proper testing of DNS64 configurations, particularly when combined with Response Policy Zones, and organizations should establish validation procedures to ensure that all configured zones have appropriate rewrite rules for both A and AAAA record types. Additionally, implementing network segmentation and access controls to limit DNS query sources can reduce the attack surface, while maintaining detailed logging of DNS queries can help detect exploitation attempts. This vulnerability serves as a reminder of the complexity inherent in DNS infrastructure and the critical need for thorough testing of edge cases in DNS server implementations.