CVE-2016-6170 in BIND
Summary
by MITRE
ISC BIND through 9.10.4-P1 allows primary DNS servers to cause a denial of service (secondary DNS server crash) via a large AXFR response, and possibly allows IXFR servers to cause a denial of service (IXFR client crash) via a large IXFR response and allows remote authenticated users to cause a denial of service (primary DNS server crash) via a large UPDATE message.
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Analysis
by VulDB Data Team • 09/01/2022
The vulnerability identified as CVE-2016-6170 affects ISC BIND versions through 9.10.4-P1 and represents a significant denial of service weakness that can be exploited by remote authenticated attackers. This flaw manifests across multiple DNS server operations including AXFR, IXFR, and UPDATE message processing, creating a comprehensive attack surface that can compromise primary and secondary DNS server operations. The vulnerability stems from inadequate input validation and memory management within the BIND DNS server implementation, specifically when handling large response messages that exceed normal operational parameters.
The technical implementation of this vulnerability involves the improper handling of oversized DNS messages during zone transfer operations and dynamic update processing. When primary DNS servers receive large AXFR responses exceeding normal size thresholds, the secondary servers attempting to process these responses can experience memory exhaustion or buffer overflow conditions that result in immediate service termination. Similarly, IXFR servers can be targeted through oversized IXFR responses that cause client crashes, while authenticated users can exploit UPDATE messages to send oversized data that triggers primary server crashes. This behavior aligns with CWE-122, which describes buffer overflow conditions, and CWE-400, which covers resource exhaustion vulnerabilities.
The operational impact of CVE-2016-6170 extends beyond simple service disruption to potentially compromise entire DNS infrastructure reliability. Organizations relying on ISC BIND for critical DNS operations face significant risk of cascading failures when primary and secondary servers become unavailable due to these denial of service conditions. The vulnerability affects both authoritative and recursive DNS server configurations, making it particularly dangerous for organizations with complex DNS hierarchies. Attackers can leverage this weakness to systematically destabilize DNS services, potentially leading to widespread internet connectivity issues, service outages, and increased attack surface for subsequent exploitation attempts. The vulnerability also aligns with ATT&CK technique T1499.004, which covers network denial of service attacks targeting DNS services.
Mitigation strategies for CVE-2016-6170 require immediate implementation of software updates to ISC BIND versions that address the specific memory handling issues in zone transfer and update processing. Organizations should implement rate limiting and size restriction policies on DNS zone transfer operations, particularly for AXFR and IXFR requests that can be configured to limit response sizes. Network administrators should also consider implementing DNS server hardening measures including limiting the number of concurrent zone transfers, implementing proper access controls to prevent unauthorized UPDATE operations, and establishing monitoring systems to detect unusual traffic patterns that may indicate exploitation attempts. Additionally, implementing DNS security extensions and proper network segmentation can help contain the impact of successful attacks while providing additional layers of protection against similar vulnerabilities.