CVE-2016-9444 in BIND
Summary
by MITRE
named in ISC BIND 9.x before 9.9.9-P5, 9.10.x before 9.10.4-P5, and 9.11.x before 9.11.0-P2 allows remote attackers to cause a denial of service (assertion failure and daemon exit) via a crafted DS resource record in an answer.
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Analysis
by VulDB Data Team • 10/28/2022
The vulnerability identified as CVE-2016-9444 represents a critical denial of service weakness within the Internet Systems Consortium BIND DNS software family. This flaw affects multiple versions including 9.9.9-P4 and earlier, 9.10.4-P4 and earlier, and 9.11.0-P1 and earlier releases. The vulnerability specifically targets the named daemon process responsible for handling DNS queries and responses within the BIND infrastructure. The flaw manifests when the daemon processes a specially crafted DS (Delegation Signer) resource record within DNS answer packets, leading to an assertion failure that ultimately causes the named process to terminate abruptly. This behavior creates a remote denial of service condition that can be exploited by attackers positioned outside the network boundary, making it particularly dangerous for public-facing DNS servers.
The technical root cause of this vulnerability lies in insufficient input validation within the DNS processing pipeline of BIND. When the named daemon encounters a malformed DS record in DNS responses, the software's internal assertion mechanisms fail to properly handle the unexpected data structure, resulting in an assertion failure that terminates the daemon process. This represents a classic buffer over-read or improper input validation issue that falls under the CWE-611 weakness category, specifically related to improper restriction of operations within a recognized operating system. The vulnerability demonstrates poor error handling practices in network protocol implementations, where the software fails to gracefully recover from malformed input rather than properly rejecting it or handling the edge case appropriately.
The operational impact of CVE-2016-9444 extends beyond simple service disruption, as it can be leveraged to create persistent denial of service conditions that affect DNS resolution for entire domains or networks. Attackers can craft malicious DNS responses containing the specially formatted DS records and inject them into the DNS resolution process, causing cascading failures that may require manual intervention to restore normal operations. This vulnerability particularly affects authoritative DNS servers that process and forward DNS responses, as well as recursive resolvers that may encounter such malformed records during normal DNS traversal operations. The attack vector requires minimal privileges and can be executed remotely, making it attractive to threat actors seeking to disrupt network services. Organizations relying on BIND for critical DNS infrastructure face significant operational risk, as the vulnerability can be exploited to create service outages that may last until the named daemon is manually restarted or the system is patched.
Mitigation strategies for CVE-2016-9444 primarily focus on immediate patching of affected BIND versions to the recommended secure releases including 9.9.9-P5, 9.10.4-P5, or 9.11.0-P2 and later. Network administrators should prioritize deployment of these patches across all affected systems, particularly those serving public DNS functions or operating as authoritative servers. Additional defensive measures include implementing DNS response validation mechanisms, deploying intrusion detection systems that can identify suspicious DNS packet patterns, and configuring network access controls to limit exposure of vulnerable DNS servers to untrusted networks. The vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, and represents a common pattern of exploitation targeting critical infrastructure components. Organizations should also consider implementing DNS traffic monitoring to detect unusual patterns that may indicate exploitation attempts, and establish incident response procedures specifically addressing DNS service disruptions. Regular vulnerability assessments and security testing of DNS infrastructure should be conducted to identify and remediate similar weaknesses in other network components that may be subject to comparable denial of service attacks.