CVE-2016-8864 in BIND
Summary
by MITRE
named in ISC BIND 9.x before 9.9.9-P4, 9.10.x before 9.10.4-P4, and 9.11.x before 9.11.0-P1 allows remote attackers to cause a denial of service (assertion failure and daemon exit) via a DNAME record in the answer section of a response to a recursive query, related to db.c and resolver.c.
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Analysis
by VulDB Data Team • 09/29/2022
The vulnerability identified as CVE-2016-8864 represents a critical denial of service flaw within the Internet Systems Consortium BIND DNS server software. This issue affects multiple versions of the BIND 9.x series, specifically targeting versions prior to 9.9.9-P4, 9.10.4-P4, and 9.11.0-P1, making it a widespread concern across various deployment environments. The flaw manifests when the DNS resolver processes certain malformed responses containing DNAME records in the answer section of recursive queries, creating a scenario where the authoritative server becomes unstable and ultimately terminates its operation.
The technical root cause of this vulnerability lies within the database handling and resolver components of BIND, specifically in the db.c and resolver.c source files. When a recursive query is processed and encounters a DNAME record in the answer section of the response, the internal assertion mechanisms fail to properly validate the record structure. This assertion failure triggers an immediate daemon exit, effectively causing the DNS service to become unavailable to legitimate clients. The vulnerability exploits the way BIND handles domain name redirection records, particularly when these records are improperly formatted or positioned within DNS responses. The flaw is classified under CWE-119 as a buffer overflow condition, where insufficient validation allows malformed data to cause system instability.
The operational impact of CVE-2016-8864 extends beyond simple service disruption, creating potential cascading failures within DNS infrastructure. Organizations relying on affected BIND versions face significant risk of service outages, particularly in environments where recursive DNS resolution is heavily utilized. The vulnerability can be exploited remotely without authentication, making it particularly dangerous as attackers can trigger the denial of service from anywhere on the internet. This flaw directly maps to ATT&CK technique T1499.004, which describes network denial of service attacks, and specifically targets the availability aspect of the CIA triad. The impact is exacerbated in large-scale deployments where a single compromised recursive resolver could affect thousands of downstream clients, potentially causing widespread internet connectivity issues.
Mitigation strategies for CVE-2016-8864 primarily involve immediate patching of affected BIND installations to versions that include the necessary code fixes. Organizations should prioritize updating their DNS infrastructure to the patched versions, ensuring that all recursive resolvers are protected against this specific attack vector. Additionally, implementing proper DNS response validation and monitoring for anomalous DNAME record patterns can provide early detection of potential exploitation attempts. Network segmentation and rate limiting of DNS queries can serve as supplementary defensive measures, though they do not address the core vulnerability. Security teams should also consider implementing intrusion detection systems capable of identifying malformed DNS responses that could indicate exploitation attempts, as the vulnerability's behavior creates distinct network traffic patterns that can be monitored and analyzed for suspicious activity.