CVE-2017-3138 in BIND
Summary
by MITRE
named contains a feature which allows operators to issue commands to a running server by communicating with the server process over a control channel, using a utility program such as rndc. A regression introduced in a recent feature change has created a situation under which some versions of named can be caused to exit with a REQUIRE assertion failure if they are sent a null command string. Affects BIND 9.9.9->9.9.9-P7, 9.9.10b1->9.9.10rc2, 9.10.4->9.10.4-P7, 9.10.5b1->9.10.5rc2, 9.11.0->9.11.0-P4, 9.11.1b1->9.11.1rc2, 9.9.9-S1->9.9.9-S9.
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Analysis
by VulDB Data Team • 11/29/2022
The vulnerability described in CVE-2017-3138 affects the Internet Systems Consortium BIND DNS server implementation, specifically targeting the named daemon's control channel functionality. This issue resides within the recursive name server component that handles DNS queries and responses across internet infrastructure. The named process operates with elevated privileges and serves as a critical component in DNS resolution for millions of internet-connected devices. The control channel mechanism allows system administrators to issue administrative commands to a running named process through utilities like rndc, enabling operations such as zone transfers, server reloads, and configuration modifications without requiring system restarts. This administrative interface represents a legitimate operational feature that provides essential management capabilities for DNS server maintenance and monitoring.
The technical flaw stems from a regression introduced in recent feature implementations within the named daemon's command processing logic. When the server receives a command string containing only null characters, the internal assertion checking mechanism fails to properly validate the input before processing. This particular assertion failure, classified as a REQUIRE assertion, indicates a fundamental assumption in the code that was violated during command handling. The vulnerability manifests as an abrupt process termination rather than graceful error handling, causing the named daemon to crash and exit. This behavior represents a denial of service condition that can be triggered remotely by any entity capable of communicating with the named control channel. The regression affects multiple versions of BIND across different release branches, indicating the issue was widespread and likely introduced during a feature development cycle that modified command parsing routines.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise DNS infrastructure reliability and availability. When the named daemon crashes due to this assertion failure, it can result in complete DNS resolution failures for affected zones, potentially affecting thousands or millions of users depending on the scope of the compromised DNS server. The vulnerability is particularly concerning because it can be exploited without authentication, as long as an attacker can establish communication with the control channel. This makes it a significant threat to DNS infrastructure security, as malicious actors could repeatedly crash DNS servers to create service outages. The vulnerability also presents potential for escalation since the named process typically runs with elevated privileges, meaning a successful exploit could potentially provide attackers with access to the underlying system resources.
Mitigation strategies for this vulnerability require immediate patching of affected BIND versions to the latest stable releases that contain the corrected assertion handling logic. System administrators should ensure all named daemons are updated to versions that have been verified to address the specific regression. Network segmentation and access control measures should be implemented to restrict access to the control channel, limiting communication to trusted administrative hosts only. The implementation of firewall rules to block unauthorized access to the named control channel ports and the use of authentication mechanisms such as TSIG keys can provide additional layers of protection. Monitoring systems should be configured to detect and alert on unexpected named daemon crashes or restarts, as these events may indicate exploitation attempts. Organizations should also implement regular security assessments of their DNS infrastructure to identify and remediate similar vulnerabilities. This vulnerability aligns with CWE-248, which covers "Uncaught Exception," and maps to ATT&CK technique T1499.004 for network denial of service attacks, demonstrating how this issue can be leveraged as part of broader attack campaigns targeting infrastructure availability.