CVE-2017-3137 in BIND
Summary
by MITRE
Mistaken assumptions about the ordering of records in the answer section of a response containing CNAME or DNAME resource records could lead to a situation in which named would exit with an assertion failure when processing a response in which records occurred in an unusual order. Affects BIND 9.9.9-P6, 9.9.10b1->9.9.10rc1, 9.10.4-P6, 9.10.5b1->9.10.5rc1, 9.11.0-P3, 9.11.1b1->9.11.1rc1, and 9.9.9-S8.
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Analysis
by VulDB Data Team • 11/29/2022
The vulnerability described in CVE-2017-3137 represents a critical flaw in the Internet Systems Consortium BIND DNS server software that stems from incorrect assumptions about DNS record ordering within response messages. This issue specifically affects the authoritative name server component named which processes DNS queries and responses. The flaw manifests when the software encounters DNS responses containing CNAME or DNAME resource records in non-standard ordering sequences, leading to an assertion failure that causes the named process to terminate abruptly. Such behavior constitutes a denial of service condition that could be exploited by remote attackers to disrupt DNS services.
The technical root cause of this vulnerability lies in the internal handling of DNS response processing logic within BIND's authoritative server implementation. When named processes DNS responses containing CNAME or DNAME records, it makes assumptions about the expected ordering of resource records within the answer section of DNS messages. Specifically, the software expects certain record types to appear in predictable sequences, but when encountering records in unusual orderings, the internal data structures and processing routines fail to handle the unexpected conditions properly. This assertion failure represents a classic software bug pattern where the program encounters an unexpected state that violates its internal assumptions, causing it to abort execution rather than gracefully handling the condition. The vulnerability is classified as a software error that violates the principle of defensive programming and proper error handling.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the availability of critical DNS infrastructure. When the named process exits due to assertion failure, it creates a complete denial of service condition that affects all DNS resolution requests handled by that server until the process is manually restarted or the system reboots. This vulnerability affects multiple versions of BIND across different release branches, indicating it represents a fundamental flaw in the codebase rather than a transient issue. The affected versions include several patch levels of BIND 9.9.x, 9.10.x, and 9.11.x series, suggesting that the flaw was present across a substantial portion of the software's release history. The vulnerability's exploitation requires only sending a specially crafted DNS response message to a vulnerable BIND server, making it particularly dangerous as it can be triggered remotely without authentication.
Mitigation strategies for CVE-2017-3137 focus primarily on applying the appropriate security patches released by the Internet Systems Consortium. Organizations should immediately upgrade to BIND versions that contain the fix for this vulnerability, typically those released after the vulnerability disclosure date. The fix addresses the root cause by implementing proper handling of DNS record ordering regardless of the sequence in which records appear in response messages. System administrators should also consider implementing additional monitoring and alerting for unexpected named process exits, as this could indicate exploitation attempts. Network-level protections such as DNS response validation and proper access controls can provide additional defense-in-depth measures. From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1499.004 for network denial of service and CWE-248 for an abnormal program termination, highlighting the importance of robust error handling in network services. Organizations should also review their DNS infrastructure for other potential similar flaws in record processing logic and implement comprehensive testing procedures to validate DNS response handling under various conditions.