CVE-1999-0275 in Windows
Summary
by MITRE
denial of service in windows nt dns servers by flooding port 53 with too many characters.
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Analysis
by VulDB Data Team • 04/16/2026
The vulnerability described in CVE-1999-0275 represents a classic denial of service attack targeting the Domain Name System infrastructure in Microsoft Windows NT operating systems. This weakness specifically affects the DNS server implementation within Windows NT versions, creating a scenario where malicious actors can disrupt network services by overwhelming the DNS server with malformed or excessively large DNS query packets on the standard DNS port 53. The vulnerability exploits the server's insufficient input validation mechanisms, allowing attackers to craft specially designed DNS requests that cause the system to consume excessive resources or crash entirely.
The technical flaw manifests through the DNS server's inadequate handling of DNS packet sizes and structure validation. When Windows NT DNS servers receive DNS queries containing an excessive number of characters or malformed packet structures, the server processing logic fails to properly validate the incoming data before attempting to parse or respond to the requests. This lack of proper input sanitization creates a condition where the server becomes overwhelmed by the malformed data, leading to resource exhaustion or system instability. The vulnerability specifically targets the UDP port 53 which is the standard port for DNS queries, making it particularly effective as it operates within the expected network protocol behavior.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire network infrastructures that rely on DNS for name resolution. When a Windows NT DNS server becomes unavailable due to this denial of service condition, all systems dependent on that server for domain name resolution will experience connectivity issues, potentially affecting email services, web browsing, file sharing, and other network-dependent applications. The attack can be executed with relatively simple tools and does not require extensive privileges, making it accessible to a wide range of threat actors. Network administrators may find it difficult to distinguish between legitimate network traffic and malicious flooding, complicating the mitigation efforts and potentially leading to extended service outages.
This vulnerability aligns with CWE-129, which addresses improper validation of input length, and represents a classic example of resource exhaustion through malformed input processing. The attack pattern corresponds to techniques described in the ATT&CK framework under the 'Resource Exhaustion' tactic, specifically targeting network services through protocol-level attacks. Organizations running Windows NT systems were particularly vulnerable as these legacy systems lacked the robust input validation and resource management features present in modern implementations. The vulnerability demonstrates the importance of proper input validation and the potential for simple protocol-level attacks to cause significant operational disruption in network infrastructure services.
Mitigation strategies for this vulnerability involve implementing proper input validation on DNS server configurations, deploying rate limiting mechanisms to prevent excessive query processing, and applying network-level filtering to block malformed DNS traffic. System administrators should configure DNS servers to enforce reasonable limits on packet sizes and implement monitoring systems to detect unusual traffic patterns. Additionally, upgrading to newer Windows versions that include improved DNS server implementations and applying security patches would provide comprehensive protection against this specific denial of service vector. Network segmentation and redundancy measures can also help minimize the impact of such attacks on overall network availability.