CVE-2016-9131 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 malformed response to an RTYPE ANY query.
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Analysis
by VulDB Data Team • 10/28/2022
The vulnerability described in CVE-2016-9131 represents a critical denial of service flaw within the Internet Systems Consortium BIND DNS server software. This vulnerability affects multiple versions of the BIND 9.x series including the 9.9.9-P4 and earlier releases, 9.10.4-P4 and earlier versions, and 9.11.0-P1 and earlier releases. The flaw manifests when the DNS daemon processes malformed responses to RTYPE ANY queries, leading to an assertion failure that causes the named daemon to terminate unexpectedly. This issue specifically impacts the authoritative DNS server functionality and can be exploited by remote attackers without authentication or prior access to the system.
The technical root cause of this vulnerability lies in insufficient input validation within the DNS response processing mechanism of BIND. When a malformed response is received in response to an ANY query, the software fails to properly validate the response data structure before attempting to process it. This lack of proper validation leads to an assertion failure, which is a programming construct designed to catch programming errors during development. The assertion failure causes the named daemon to exit abruptly, resulting in a complete denial of service for the affected DNS server. The vulnerability is classified under CWE-129 as an insufficient input validation issue, where the system fails to properly validate the range, size, or format of input data before processing it. This flaw demonstrates poor error handling and input sanitization practices that are fundamental to secure software development.
The operational impact of CVE-2016-9131 is severe and can significantly disrupt network services that depend on DNS resolution. When exploited, the vulnerability causes the DNS server to crash and restart, leading to temporary unavailability of DNS services for all clients relying on that server. This can result in cascading failures throughout network infrastructure, as applications and services that depend on DNS resolution become inaccessible. The vulnerability affects both primary and secondary DNS servers, making it particularly dangerous for organizations that rely on DNS for critical infrastructure operations. Attackers can easily exploit this vulnerability by crafting specially malformed DNS responses to ANY queries, requiring minimal technical expertise and no authentication credentials. This makes the vulnerability particularly attractive to threat actors seeking to disrupt network services through simple denial of service attacks.
Organizations affected by this vulnerability should prioritize immediate patching of their BIND installations to versions 9.9.9-P5, 9.10.4-P5, or 9.11.0-P2, respectively, depending on their current software version. The patch implementation should be followed by comprehensive testing to ensure that the upgrade does not introduce compatibility issues with existing DNS configurations. Network administrators should also implement monitoring solutions to detect unusual DNS server behavior or frequent restarts that might indicate exploitation attempts. Additional mitigations include implementing DNS response validation mechanisms, configuring firewalls to limit DNS query types, and establishing redundant DNS server configurations to minimize service disruption. This vulnerability aligns with ATT&CK technique T1499.004 which describes denial of service through resource exhaustion or service interruption. The vulnerability also relates to ATT&CK tactic TA0040 which encompasses defense evasion techniques, as the exploitation can be used to disrupt security monitoring systems that depend on DNS resolution for their operation. Organizations should also consider implementing intrusion detection systems that can identify and alert on malformed DNS responses that match the patterns associated with this specific vulnerability.