CVE-2019-6465 in BIND
Summary
by MITRE
Controls for zone transfers may not be properly applied to Dynamically Loadable Zones (DLZs) if the zones are writable Versions affected: BIND 9.9.0 -> 9.10.8-P1, 9.11.0 -> 9.11.5-P2, 9.12.0 -> 9.12.3-P2, and versions 9.9.3-S1 -> 9.11.5-S3 of BIND 9 Supported Preview Edition. Versions 9.13.0 -> 9.13.6 of the 9.13 development branch are also affected. Versions prior to BIND 9.9.0 have not been evaluated for vulnerability to CVE-2019-6465.
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Analysis
by VulDB Data Team • 05/21/2025
The vulnerability described in CVE-2019-6465 represents a critical security flaw in the Berkeley Internet Name Domain (BIND) software that affects multiple versions across different release branches. This issue specifically targets the handling of zone transfers within Dynamically Loadable Zones (DLZs), which are a feature that allows DNS zones to be loaded dynamically from external sources rather than being statically configured in the main configuration file. The flaw arises from improper enforcement of access controls during zone transfer operations, potentially allowing unauthorized parties to access or manipulate DNS data that should remain restricted.
The technical implementation of this vulnerability stems from a failure in the authorization mechanisms that govern zone transfer operations within DLZ configurations. When DNS servers process zone transfers for writable zones, the security controls that typically restrict these operations based on source IP addresses, TSIG authentication, or other access control measures may be bypassed or inadequately enforced. This occurs specifically in scenarios where zones are loaded dynamically rather than being statically defined, creating a gap in the security model that attackers can exploit. The flaw affects the core DNS server functionality and operates at the protocol level, making it particularly dangerous as it can impact the integrity and confidentiality of DNS data across affected installations.
The operational impact of CVE-2019-6465 extends beyond simple data exposure, potentially enabling attackers to perform unauthorized zone transfers that could reveal sensitive information about network infrastructure, internal hostnames, and DNS configurations. This vulnerability can be leveraged to conduct reconnaissance activities, facilitate further attacks, or even enable denial-of-service conditions by manipulating DNS records. The widespread adoption of BIND across internet infrastructure means that exploitation of this vulnerability could affect numerous organizations simultaneously, potentially compromising large-scale DNS deployments. The vulnerability's presence in multiple release branches including stable releases and preview editions indicates a systemic issue that required coordinated patching across the software lifecycle.
Mitigation strategies for this vulnerability involve implementing immediate software updates to versions that contain the necessary security patches, as well as reviewing and strengthening DNS security configurations. Organizations should verify that their DLZ configurations properly enforce access controls and consider implementing additional monitoring for unusual zone transfer activities. The vulnerability aligns with CWE-284, which addresses improper access control, and can be mapped to ATT&CK techniques related to credential access and defense evasion through DNS tunneling and reconnaissance activities. Network administrators should also consider implementing firewall rules that restrict zone transfer operations to trusted sources only, and conduct thorough security audits of their DNS infrastructure to ensure that all zones are properly configured with appropriate access controls.