CVE-2010-0231 in Windows
Summary
by MITRE
The SMB implementation in the Server service in Microsoft Windows 2000 SP4, Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista Gold, SP1, and SP2, Windows Server 2008 Gold, SP2, and R2, and Windows 7 does not use a sufficient source of entropy, which allows remote attackers to obtain access to files and other SMB resources via a large number of authentication requests, related to server-generated challenges, certain "duplicate values," and spoofing of an authentication token, aka "SMB NTLM Authentication Lack of Entropy Vulnerability."
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Analysis
by VulDB Data Team • 04/30/2026
The SMB NTLM Authentication Lack of Entropy Vulnerability represents a critical security flaw in Microsoft Windows operating systems that undermines the integrity of the Server Message Block authentication mechanism. This vulnerability specifically targets the Server service component that handles SMB protocol communications, affecting a wide range of Microsoft products from Windows 2000 through Windows 7. The issue stems from the insufficient entropy in the challenge-response authentication process, which is a fundamental component of the NTLM authentication protocol used by Windows systems. The vulnerability operates at the network protocol level, making it particularly dangerous as it can be exploited remotely without requiring any prior authentication or privileges.
The technical flaw manifests in the way Windows generates server-generated challenges during the NTLM authentication process. When a client attempts to authenticate to a Windows server using SMB, the server creates a random challenge value that the client must respond to correctly. In affected versions, this challenge generation process does not utilize sufficient randomness or entropy, resulting in predictable or repetitive challenge values. This weakness allows attackers to perform brute force attacks by sending numerous authentication requests and analyzing the responses to identify patterns in the challenge generation. The vulnerability is particularly concerning because it enables attackers to spoof authentication tokens and gain unauthorized access to shared resources, files, and system components through repeated authentication attempts that exploit the predictable nature of the challenge values.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as it can lead to complete system compromise and lateral movement within network environments. Attackers can leverage this weakness to escalate privileges, access sensitive data, and potentially establish persistent access to target systems. The vulnerability is especially dangerous in enterprise environments where SMB is widely used for file sharing and network communication, as it can enable attackers to move laterally through networks by compromising individual systems and using the gained access to target other systems. The attack vector requires only network connectivity to the target system, making it particularly attractive to threat actors who can exploit it from external networks or internal network positions.
Security professionals should recognize this vulnerability as a classic example of insufficient entropy in cryptographic systems, which aligns with CWE-330 and CWE-331 weakness categories that address inadequate randomness in security protocols. The vulnerability also maps to several ATT&CK techniques including T1110.001 (Brute Force: Password Guessing) and T1078.002 (Valid Accounts: Domain Accounts) as attackers can use predictable challenges to bypass authentication mechanisms. Organizations should implement immediate mitigations including applying the relevant Microsoft security updates that address the entropy issue in challenge generation, configuring SMB security settings to disable vulnerable authentication methods, and implementing network segmentation to limit the impact of successful exploitation. Additionally, monitoring for unusual authentication patterns and implementing intrusion detection systems can help identify exploitation attempts before they result in successful unauthorized access to critical resources.