CVE-2016-9147 in BIND
Summary
by MITRE
named in ISC BIND 9.9.9-P4, 9.9.9-S6, 9.10.4-P4, and 9.11.0-P1 allows remote attackers to cause a denial of service (assertion failure and daemon exit) via a response containing an inconsistency among the DNSSEC-related RRsets.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/28/2022
The vulnerability identified as CVE-2016-9147 affects the Internet Systems Consortium BIND DNS server software across multiple versions including 9.9.9-P4, 9.9.9-S6, 9.10.4-P4, and 9.11.0-P1. This represents a critical denial of service flaw that can be exploited by remote attackers to disrupt DNS services. The vulnerability specifically targets the DNSSEC validation mechanisms within BIND, which are designed to provide authentication and data integrity for DNS responses. When a maliciously crafted DNS response is processed by the affected BIND server, it triggers an assertion failure that causes the daemon to terminate unexpectedly, effectively rendering the DNS service unavailable to legitimate users.
The technical flaw stems from inadequate validation of DNSSEC-related resource record sets within the DNS response processing pipeline. When the BIND server receives a DNS response containing inconsistent DNSSEC records, the internal validation logic fails to properly handle this edge case, leading to an assertion failure. This assertion failure occurs within the DNSSEC validation subsystem, specifically in how the server processes and verifies the relationships between different DNSSEC record types such as RRSIG, DS, and DNSKEY records. The inconsistency among these RRsets creates a scenario where the server's internal state becomes invalid, triggering the assertion that causes the daemon to exit. This behavior aligns with CWE-248, which describes improper exception handling in software systems, and represents a classic example of how malformed input can cause program termination through assertion failures rather than graceful error handling.
The operational impact of CVE-2016-9147 extends beyond simple service disruption to potentially compromise the reliability and availability of DNS infrastructure. Organizations relying on affected BIND versions face the risk of sustained denial of service attacks that can take down critical DNS services, affecting thousands of domains and applications that depend on proper DNS resolution. The vulnerability is particularly dangerous because it can be triggered by simply receiving a malicious DNS response, making it possible for attackers to cause service disruption without requiring any authentication or privileged access. This makes the attack surface extremely broad and difficult to defend against through traditional network security measures. From an attacker perspective, this vulnerability maps to ATT&CK technique T1499.004 which involves network denial of service attacks, and the attack can be executed through DNS cache poisoning or other means of delivering malformed DNS responses to the target server.
Mitigation strategies for CVE-2016-9147 primarily involve upgrading to patched versions of BIND software, specifically versions that contain the necessary fixes for the DNSSEC validation logic. Organizations should also implement defensive measures such as limiting DNS server exposure to untrusted networks, implementing proper rate limiting on DNS queries, and monitoring for unusual patterns in DNS response processing that might indicate exploitation attempts. Network administrators should consider implementing DNSSEC validation policies that can help detect and prevent malformed DNSSEC responses from being processed by the authoritative servers. Additionally, organizations should regularly test their DNS infrastructure against known vulnerable configurations and maintain up-to-date security patches for all DNS-related software components. The vulnerability highlights the importance of robust input validation and proper error handling in critical infrastructure software, emphasizing that DNS servers must be resilient to malformed inputs without compromising service availability.