CVE-2000-1139 in Exchange
Summary
by MITRE
The installation of Microsoft Exchange 2000 before Rev. A creates a user account with a known password, which could allow attackers to gain privileges, aka the "Exchange User Account" vulnerability.
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Analysis
by VulDB Data Team • 10/11/2025
The CVE-2000-1139 vulnerability represents a critical security flaw in Microsoft Exchange 2000 Server installations prior to revision A, where the software automatically creates a user account with a predictable and well-known password. This vulnerability falls under the category of weak credential management and insecure default configurations, which are commonly classified as CWE-798 (Use of Hard-coded Credentials) and CWE-259 (Use of Hard-coded Password). The flaw stems from Microsoft's installation process that provisions a default account named "Exchange" or similar with a default password that has been widely documented and shared within security communities, creating an inherent backdoor access vector for malicious actors.
The technical implementation of this vulnerability exploits the fundamental principle of least privilege by creating a privileged account with easily guessable authentication credentials. When Exchange 2000 Server is installed without applying the necessary security patches or updates, the system automatically generates this account with a default password that remains unchanged in many deployments. This default account typically possesses administrative privileges within the Exchange environment, allowing attackers who discover or guess the password to gain full control over email services, access to mailboxes, and potentially escalate their privileges to system-level access. The vulnerability is particularly dangerous because it occurs during the initial installation phase, meaning organizations may unknowingly deploy systems with these insecure default credentials.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it creates a persistent security risk that can be exploited across multiple deployment scenarios. Attackers can leverage this vulnerability through various attack vectors including network reconnaissance, password guessing, and credential reuse attacks, all of which are catalogued under the MITRE ATT&CK framework within the credential access and privilege escalation domains. The vulnerability affects organizations that have not applied the security update released by Microsoft, and it remains exploitable even if the system is otherwise properly configured, as the default account persists regardless of other security measures. This creates a significant risk for email infrastructure, as the compromised account can be used to read sensitive communications, modify email content, create new user accounts, or establish persistence within the network.
Organizations should implement comprehensive mitigation strategies that include immediate patching of all Exchange 2000 servers to revision A or later, followed by verification that the default account has been properly secured or removed from the system. The remediation process should involve disabling or deleting the vulnerable default account, implementing strong password policies for all user accounts, and conducting thorough inventory audits to ensure no systems remain with insecure default credentials. Security monitoring should be enhanced to detect attempts to authenticate using default account names and passwords, and network segmentation should be implemented to limit access to Exchange services. Additionally, organizations should establish robust change management processes to ensure that all security updates are applied promptly and that default accounts are properly reviewed and secured during system deployment. This vulnerability demonstrates the critical importance of proper initial configuration and timely patch management in maintaining secure email infrastructure, as it represents a fundamental failure in the security baseline of the Microsoft Exchange platform.