CVE-2000-0328 in Windows
Summary
by MITRE
Windows NT 4.0 generates predictable random TCP initial sequence numbers (ISN), which allows remote attackers to perform spoofing and session hijacking.
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Analysis
by VulDB Data Team • 04/19/2026
The vulnerability described in CVE-2000-0328 represents a critical weakness in the Windows NT 4.0 operating system's implementation of the Transmission Control Protocol. This flaw stems from the operating system's inability to generate sufficiently random initial sequence numbers for TCP connections, creating a predictable pattern that adversaries can exploit to gain unauthorized access to network sessions. The issue directly impacts the fundamental security mechanisms that govern TCP communication, specifically the sequence number generation process that ensures the integrity and authenticity of data transmission between hosts.
The technical flaw manifests in the cryptographic randomness of TCP initial sequence numbers, which should be unpredictable to prevent attackers from guessing valid sequence numbers for establishing forged connections. Windows NT 4.0's implementation fails to utilize proper random number generation algorithms, resulting in sequence numbers that follow discernible patterns or are easily reproducible through analysis of network traffic. This weakness falls under the category of weak cryptographic randomness as defined by CWE-330, where insufficient entropy in random number generation creates predictable outputs that compromise security protocols.
The operational impact of this vulnerability extends beyond simple network interference to enable sophisticated session hijacking attacks that can completely compromise network communications. Remote attackers can leverage the predictable sequence numbers to inject malicious data into existing TCP sessions, redirect traffic, or even take full control of established connections without requiring authentication. This vulnerability particularly affects systems running Windows NT 4.0 in enterprise environments where TCP-based services such as web servers, email servers, and database connections are prevalent, making it a significant threat to network infrastructure security.
The exploitation of this vulnerability aligns with several techniques documented in the MITRE ATT&CK framework, specifically targeting the T1071.004 tactic for application layer protocol usage and T1566 for credential access through network sniffing and session hijacking. Organizations with Windows NT 4.0 systems are particularly vulnerable to man-in-the-middle attacks where attackers can predict sequence numbers and establish legitimate-looking connections to intercept or manipulate data flows. The vulnerability also represents a failure in the principle of least privilege, as the predictable nature of sequence numbers undermines the security model that relies on unpredictable session identifiers to maintain connection integrity.
Mitigation strategies for this vulnerability require immediate system updates and patches to address the underlying random number generation implementation. Organizations should implement network monitoring solutions to detect anomalous TCP sequence number patterns and consider deploying TCP sequence number randomization mechanisms at the network level. The recommended approach includes upgrading to supported operating systems that implement proper cryptographic random number generation, as Windows NT 4.0 reached end-of-life and no longer receives security updates. Network segmentation and firewall rules can provide additional layers of protection, while regular security assessments should verify that sequence number generation meets current cryptographic standards and that no legacy systems remain vulnerable to this specific class of attack.