CVE-2002-1509 in Linux
Summary
by MITRE
A patch for shadow-utils 20000902 causes the useradd command to create a mail spool files with read/write privileges of the new user s group (mode 660), which allows other users in the same group to read or modify the new user s incoming email.
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Analysis
by VulDB Data Team • 07/19/2019
The vulnerability described in CVE-2002-1509 represents a significant security flaw in the shadow-utils package version 20000902 that affected Unix and Linux systems during the early 2000s. This issue emerged from a patch implementation that inadvertently altered the default permissions assigned to mail spool files created by the useradd command, creating a privilege escalation vector through group membership. The problem directly impacts the principle of least privilege by allowing unauthorized access to sensitive user email communications through group-based permissions rather than individual user permissions.
The technical flaw manifests when the useradd command creates mail spool files with mode 660 permissions, which grants read and write access to both the user and the group associated with that user account. This permission scheme violates the expected security model where mail spool files should be accessible only to the specific user who owns them. The vulnerability specifically affects the shadow-utils package, which provides essential user management utilities including useradd, userdel, and usermod commands that handle user account creation and management in Unix-like operating systems. The flaw demonstrates poor implementation of access control mechanisms and highlights the importance of careful permission management in system utilities that handle sensitive data.
The operational impact of this vulnerability extends beyond simple information disclosure to create potential for email manipulation and unauthorized access to user communications. Any user within the same group as the affected user can read or modify incoming email messages, which could lead to data theft, impersonation attacks, or the compromise of sensitive information contained in email communications. This vulnerability particularly affects multi-user systems where users may belong to shared groups for legitimate purposes, yet the mail spool file permissions create an unintended escalation path. The issue represents a classic case of insufficient privilege separation in system utilities, where administrative changes to default behavior inadvertently weaken security boundaries.
Security mitigations for this vulnerability require immediate patching of the shadow-utils package to restore proper mail spool file permissions, typically setting them to mode 600 to ensure only the owner can access the files. System administrators should also conduct thorough audits of existing user accounts and mail spool files to identify any compromised access patterns. The vulnerability aligns with CWE-276, which describes improper file permissions, and demonstrates the importance of maintaining proper access controls in system utilities. From an ATT&CK perspective, this vulnerability could be leveraged as a privilege escalation technique, potentially enabling adversaries to access sensitive communications and use that information for further attacks. Organizations should implement regular security assessments of system utilities and maintain updated security patches to prevent such regressions in access control mechanisms.