CVE-2011-1966 in Windows
Summary
by MITRE
The DNS server in Microsoft Windows Server 2008 SP2, R2, and R2 SP1 does not properly handle NAPTR queries that trigger recursive processing, which allows remote attackers to execute arbitrary code via a crafted query, aka "DNS NAPTR Query Vulnerability."
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Analysis
by VulDB Data Team • 03/19/2021
The DNS NAPTR Query Vulnerability identified as CVE-2011-1966 represents a critical remote code execution flaw in Microsoft Windows Server 2008 and its subsequent service packs. This vulnerability specifically targets the Domain Name System server component that handles Network Access Protection NAPTR (Name Authority Pointer) queries, which are used in telecommunications and internet protocols to define services available for a domain. The flaw occurs when the DNS server receives specially crafted NAPTR queries that trigger recursive processing behavior, creating a condition where memory corruption can occur during query handling. The vulnerability stems from improper validation of NAPTR record data structures and insufficient bounds checking during recursive query resolution processes.
The technical exploitation of this vulnerability leverages the recursive DNS processing mechanism that occurs when a DNS server receives a query for a domain that requires additional resolution steps. When a malformed NAPTR query is processed, the server's internal memory management routines fail to properly validate the query parameters, leading to buffer overflow conditions or other memory corruption scenarios. This memory corruption can be manipulated by remote attackers to overwrite critical memory locations, potentially allowing execution of arbitrary code with the privileges of the DNS server process. The vulnerability is particularly dangerous because it can be triggered without authentication, making it an ideal candidate for automated exploitation campaigns. According to CWE classification, this represents a weakness in the input validation and memory management aspects of the software, specifically categorized under CWE-121 for heap-based buffer overflow conditions.
The operational impact of this vulnerability extends beyond simple remote code execution, as successful exploitation can lead to complete system compromise and persistent access within network environments. Attackers can leverage this vulnerability to establish backdoors, escalate privileges, or use the compromised DNS server as a pivot point for further attacks against internal network resources. The DNS server typically runs with elevated privileges and has access to critical network infrastructure, making successful exploitation particularly damaging. Organizations relying on Windows Server DNS services for network operations face significant risk, as the vulnerability can be exploited by external attackers without requiring any prior access to the network. This vulnerability aligns with ATT&CK technique T1071.004 for application layer protocol usage and T1059.001 for command and scripting interpreter execution, as attackers can use the compromised system to run malicious commands and scripts.
Mitigation strategies for CVE-2011-1966 focus on immediate patch deployment, network segmentation, and query filtering mechanisms. Microsoft released security update MS11-046 that addressed this vulnerability through improved input validation and memory management in the DNS server component. Organizations should implement network-level protections such as DNS query filtering to block malformed NAPTR queries and restrict recursive DNS processing for external clients. The implementation of DNS security extensions including DNSSEC can provide additional protection layers against malformed query exploitation. Network administrators should also consider disabling unnecessary DNS server features and implementing strict access controls to limit exposure. Additionally, monitoring systems should be configured to detect unusual DNS query patterns that may indicate exploitation attempts, particularly focusing on NAPTR query processing anomalies. The vulnerability demonstrates the importance of proper input validation and memory safety practices as outlined in secure coding guidelines and represents a classic example of how recursive processing can introduce security risks when not properly bounded and validated.