CVE-2009-0696 in BIND
Summary
by MITRE
The dns_db_findrdataset function in db.c in named in ISC BIND 9.4 before 9.4.3-P3, 9.5 before 9.5.1-P3, and 9.6 before 9.6.1-P1, when configured as a master server, allows remote attackers to cause a denial of service (assertion failure and daemon exit) via an ANY record in the prerequisite section of a crafted dynamic update message.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 12/23/2025
The vulnerability described in CVE-2009-0696 represents a critical denial of service flaw within the Internet Systems Consortium BIND DNS server software. This issue affects multiple versions of BIND 9 including 9.4 before 9.4.3-P3, 9.5 before 9.5.1-P3, and 9.6 before 9.6.1-P1 when configured as a master server. The vulnerability stems from improper handling of dynamic update messages containing ANY records in the prerequisite section, which can trigger assertion failures and subsequently cause the named daemon to terminate unexpectedly. This flaw operates at the application layer and specifically targets the DNS server's database management functionality.
The technical implementation of this vulnerability occurs within the dns_db_findrdataset function located in the db.c source file of the BIND software. When a master server receives a crafted dynamic update message containing an ANY record in the prerequisite section, the function fails to properly validate or handle this specific record type. The assertion failure that results from this improper handling causes the named daemon to crash and exit, effectively removing the DNS service from operation. This behavior constitutes a classic denial of service condition where legitimate service availability is compromised through malicious input manipulation. The vulnerability is particularly dangerous because it can be exploited remotely without requiring authentication or special privileges.
The operational impact of CVE-2009-0696 extends beyond simple service interruption to potentially disrupt critical network infrastructure dependencies. DNS servers serve as foundational components for internet connectivity, and their failure can cascade through entire networks, affecting email services, web browsing, and other applications that depend on name resolution. When a master DNS server becomes unavailable due to this assertion failure, it can prevent legitimate dynamic updates from being processed and may cause secondary DNS servers to fail in their operations. The vulnerability demonstrates a weakness in input validation and error handling within the DNS server's update processing pipeline, making it particularly attractive to attackers seeking to disrupt network services. This flaw aligns with CWE-248, which describes an unchecked exception vulnerability, and represents a failure in proper error handling mechanisms.
Mitigation strategies for this vulnerability require immediate patching of affected BIND versions to the recommended security releases. Organizations should prioritize updating their DNS server software to versions 9.4.3-P3, 9.5.1-P3, or 9.6.1-P1 respectively, as these releases contain the necessary code modifications to properly handle ANY records in dynamic update messages. Network administrators should also implement monitoring solutions to detect unusual dynamic update patterns that might indicate exploitation attempts. Additional defensive measures include configuring access controls to limit dynamic update permissions to trusted sources only, implementing rate limiting on update requests, and establishing redundant DNS server configurations to maintain service availability during potential disruptions. The ATT&CK framework categorizes this vulnerability under the T1499.004 technique for network denial of service, emphasizing the importance of proper input validation and error handling in preventing such attacks.