CVE-2023-5679 in BIND
Summary
by MITRE • 02/13/2024
A bad interaction between DNS64 and serve-stale may cause `named` to crash with an assertion failure during recursive resolution, when both of these features are enabled. This issue affects BIND 9 versions 9.16.12 through 9.16.45, 9.18.0 through 9.18.21, 9.19.0 through 9.19.19, 9.16.12-S1 through 9.16.45-S1, and 9.18.11-S1 through 9.18.21-S1.
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Analysis
by VulDB Data Team • 03/29/2025
The vulnerability described in CVE-2023-5679 represents a critical flaw in the Internet Systems Consortium BIND DNS server that manifests through an interaction between two advanced DNS features. This issue specifically targets the recursive resolution process within named, the primary DNS server software used by organizations worldwide. The flaw occurs when both DNS64 and serve-stale functionalities are simultaneously enabled, creating a condition where the server experiences an assertion failure leading to a complete crash. DNS64 is a mechanism that enables IPv6-only networks to access IPv4 services by synthesizing IPv4 addresses, while serve-stale allows the server to continue serving stale data when the primary source is unavailable. The combination of these features creates an unexpected state where the internal assertion checks fail, causing the named process to terminate abruptly.
The technical implementation of this vulnerability stems from improper state management within the recursive resolution logic when handling DNS queries that traverse both DNS64 translation and serve-stale mechanisms. When a query is processed through this specific combination, the server's internal data structures become inconsistent, triggering an assertion failure that is designed to catch programming errors but in this case represents an actual bug rather than an error condition. The assertion failure occurs during the recursive resolution phase where the server attempts to determine whether to serve stale data or pursue fresh resolution, creating a race condition or state inconsistency that was not properly accounted for in the code logic. This type of flaw falls under CWE-248, which addresses the exposure of an exception to an unexpected environment, and can be classified as an improper handling of a control structure in the context of software reliability.
The operational impact of this vulnerability is severe for organizations relying on BIND 9 servers with these features enabled. A successful exploitation of this vulnerability results in a denial of service condition where the named process crashes and requires manual intervention to restart, potentially disrupting DNS resolution services for all clients relying on that server. The crash affects the availability of DNS services and can be particularly damaging in environments where DNS infrastructure is critical for network operations, such as enterprise networks, cloud services, or internet service providers. The vulnerability affects multiple stable release lines of BIND 9, indicating a widespread impact across different versions that organizations may have deployed in production environments. The specific version ranges mentioned suggest that this issue has been present for several releases, making it a long-standing problem that organizations may have been unknowingly exposed to.
Organizations should prioritize immediate patching of affected BIND 9 installations to address this vulnerability, as the crash can be exploited to cause service disruption without requiring any special privileges or authentication. The recommended mitigation involves upgrading to patched versions of BIND 9 that resolve the interaction between DNS64 and serve-stale features, or temporarily disabling one or both features if immediate patching is not feasible. Security teams should also implement monitoring for assertion failures in their DNS server logs, as these may indicate attempts to trigger the vulnerability or serve as early warning signs of potential exploitation. This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a legitimate security concern that can be leveraged by adversaries seeking to disrupt network services through DNS infrastructure. The issue demonstrates the complexity of modern DNS implementations where multiple advanced features interact in unexpected ways, highlighting the importance of thorough testing and validation of feature combinations in production environments.