CVE-1999-0825 in UnixWare
Summary
by MITRE
The default permissions for UnixWare /var/mail allow local users to read and modify other users' mail.
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Analysis
by VulDB Data Team • 04/19/2026
The vulnerability described in CVE-1999-0825 represents a classic privilege escalation issue affecting UnixWare operating systems where the default file permissions for the /var/mail directory were inadequately configured. This flaw allowed local users to gain unauthorized access to other users' email messages and modify their mail content, creating a significant security risk within multi-user environments. The issue stems from improper access control mechanisms that failed to enforce proper isolation between user mailboxes, effectively breaking the fundamental security principle of user privacy and data integrity.
The technical root cause of this vulnerability lies in the default permission settings applied to the /var/mail directory, which typically contained individual mail spool files for each user account. When these directories were configured with overly permissive permissions such as world-readable and world-writable modes, any local user could access the mail files of other users through standard file system operations. This configuration violates the principle of least privilege and creates an attack surface that allows malicious users to read sensitive communications, modify mail content, or even delete messages from other accounts. The vulnerability specifically impacts UnixWare systems where the mail spool directory structure was not properly secured against unauthorized access attempts.
The operational impact of CVE-1999-0825 extends beyond simple privacy violations to encompass potential data integrity compromises and information disclosure risks. Local users could exploit this vulnerability to access confidential communications, potentially including personal information, business correspondence, or sensitive organizational data. The ability to modify mail content introduces additional risks such as message tampering, which could be used for social engineering attacks or to manipulate communication flows within an organization. This vulnerability is particularly concerning in environments where multiple users share a single system, as it undermines the trust model that should exist between users and system administrators. The risk is amplified when considering that such access could be leveraged to gather intelligence about other users or to disrupt communication channels within an organization.
Mitigation strategies for this vulnerability should focus on proper permission configuration and access control enforcement. System administrators must ensure that the /var/mail directory and its constituent mail files are configured with appropriate permissions that restrict access to authorized users only, typically requiring owner-only read and write permissions. This aligns with the security principle outlined in the CWE-276 standard for improper file permissions, which specifically addresses inadequate access control for file system objects. Additionally, implementing proper auditing mechanisms can help detect unauthorized access attempts to mail directories. Organizations should also consider implementing the principle of least privilege as defined in the ATT&CK framework under the privilege escalation category, ensuring that users have only the minimum access necessary for their legitimate system usage. Regular security audits and permission reviews should be conducted to prevent similar issues from reoccurring, particularly in legacy Unix systems where default configurations may not meet current security standards.