CVE-2016-1284 in BIND
Summary
by MITRE
rdataset.c in ISC BIND 9 Supported Preview Edition 9.9.8-S before 9.9.8-S5, when nxdomain-redirect is enabled, allows remote attackers to cause a denial of service (REQUIRE assertion failure and daemon exit) via crafted flag values in a query.
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Analysis
by VulDB Data Team • 10/15/2024
The vulnerability identified as CVE-2016-1284 affects ISC BIND 9 Supported Preview Edition versions 9.9.8-S through 9.9.8-S4, representing a critical denial of service flaw that can be exploited remotely by attackers. This vulnerability specifically manifests when the nxdomain-redirect feature is enabled within the DNS server configuration, creating a scenario where malformed flag values in DNS queries can trigger a REQUIRE assertion failure that ultimately causes the BIND daemon to terminate unexpectedly. The issue stems from insufficient input validation in the rdataset.c component of the software, which fails to properly handle crafted flag values that would normally be rejected by standard DNS parsing mechanisms.
The technical exploitation of this vulnerability occurs through the manipulation of DNS query flag fields, particularly targeting the nxdomain-redirect functionality that is designed to redirect queries for non-existent domains to configured alternative servers. When an attacker crafts a DNS query with specific malformed flag values and sends it to a vulnerable BIND server with nxdomain-redirect enabled, the software's internal assertion checking mechanism fails to properly validate the incoming data. This failure results in a REQUIRE assertion that triggers an immediate daemon exit, effectively bringing the DNS service offline and preventing legitimate queries from being processed. The vulnerability is classified as a CWE-129 Improper Validation of Array Index, as it involves the improper handling of data that should be validated before being processed in memory operations.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged to create sustained denial of service conditions that affect DNS resolution for entire networks or domains. Organizations relying on affected BIND versions may experience complete DNS outages, potentially affecting critical infrastructure services, web applications, and email systems that depend on proper DNS resolution. The vulnerability's remote exploitability means that attackers can target these systems from anywhere on the internet without requiring local access or authentication credentials. This makes it particularly dangerous in environments where DNS servers are directly exposed to external traffic, as the attack can be executed with minimal effort and technical knowledge required.
Security practitioners should immediately implement mitigations including updating to BIND 9.9.8-S5 or later versions where this vulnerability has been patched, disabling the nxdomain-redirect feature if it is not essential for operations, or implementing network-level protections such as firewall rules that limit DNS query traffic from untrusted sources. The ATT&CK framework categorizes this vulnerability under T1499.004 Network Denial of Service, as it enables attackers to disrupt network services through deliberate exploitation of software flaws. Organizations should also consider implementing monitoring solutions that can detect abnormal daemon termination patterns and unusual DNS query patterns that may indicate exploitation attempts. Additionally, regular vulnerability assessments and penetration testing should be conducted to identify other potential weaknesses in DNS infrastructure that could be exploited in similar fashion, ensuring comprehensive protection against this and related classes of denial of service vulnerabilities.
The root cause analysis reveals that this vulnerability represents a failure in the software's defensive programming practices, specifically the lack of proper input validation and error handling for DNS flag fields. The REQUIRE assertion mechanism, designed to catch programming errors during development, was inadvertently triggered by legitimate but malformed network traffic, demonstrating the importance of robust input validation in security-critical systems. This flaw underscores the necessity of thorough testing procedures including fuzzing and boundary condition testing for network services that process untrusted data, as well as the importance of maintaining up-to-date software versions that contain security patches addressing known vulnerabilities in the DNS infrastructure stack.