CVE-2023-5517 in BIND
Summary
by MITRE • 02/13/2024
A flaw in query-handling code can cause `named` to exit prematurely with an assertion failure when:
- `nxdomain-redirect ;` is configured, and - the resolver receives a PTR query for an RFC 1918 address that would normally result in an authoritative NXDOMAIN response. This issue affects BIND 9 versions 9.12.0 through 9.16.45, 9.18.0 through 9.18.21, 9.19.0 through 9.19.19, 9.16.8-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 • 11/15/2024
The vulnerability described in CVE-2023-5517 represents a critical assertion failure in the named resolver component of BIND 9 DNS software that can lead to premature service termination. This flaw specifically manifests when the resolver encounters a particular combination of configuration settings and query types, creating a scenario where the service becomes unstable and potentially unavailable to legitimate users. The issue arises from improper handling of query responses in the context of NXDOMAIN redirection, which is a fundamental aspect of DNS resolution behavior when authoritative servers cannot locate requested records.
The technical root cause stems from the query-handling code within named that fails to properly manage the interaction between nxdomain-redirect configuration and PTR query processing for RFC 1918 addresses. RFC 1918 addresses refer to private IP ranges that are not globally routable and typically result in NXDOMAIN responses when queried. When the nxdomain-redirect directive is enabled, the system attempts to redirect queries for non-existent domains to alternative destinations, but this redirection logic conflicts with the expected behavior for private address space queries. This conflict creates an assertion failure that causes the named process to terminate abruptly, effectively disrupting DNS service availability.
The operational impact of this vulnerability extends beyond simple service disruption to potentially enable denial-of-service attacks against DNS infrastructure. Attackers could exploit this weakness by crafting specific PTR queries for RFC 1918 addresses while the server has nxdomain-redirect configured, leading to service unavailability that could affect downstream applications and users relying on DNS resolution. The vulnerability affects multiple release branches of BIND 9, indicating it is a persistent issue that spans several versions and could impact organizations with different deployment scenarios. This widespread affected scope increases the potential attack surface and makes the vulnerability particularly concerning for large-scale DNS deployments.
The flaw aligns with CWE-248, which describes an "Uncaught Exception" scenario where a program fails to handle exceptional conditions properly, leading to unexpected termination. This categorization reflects the assertion failure that occurs when the resolver encounters the specific query pattern, demonstrating how improper error handling can result in complete service failure. From an ATT&CK perspective, this vulnerability maps to T1499.004, which covers "Endpoint Denial of Service" through resource consumption or process termination, as the assertion failure effectively terminates the DNS service process. Organizations should prioritize patching affected systems, as the vulnerability provides attackers with a straightforward method to disrupt DNS services. The recommended mitigation involves updating to patched versions of BIND 9, specifically versions that address the assertion handling logic in query processing, and carefully reviewing nxdomain-redirect configurations to minimize exposure to this specific attack vector.