CVE-1999-1409 in NetBSD
Summary
by MITRE
The at program in IRIX 6.2 and NetBSD 1.3.2 and earlier allows local users to read portions of arbitrary files by submitting the file to at with the -f argument, which generates error messages that at sends to the user via e-mail.
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Analysis
by VulDB Data Team • 12/19/2024
The vulnerability described in CVE-1999-1409 represents a significant privilege escalation and information disclosure flaw within the at program on Unix-like systems. This vulnerability affects specific versions of IRIX 6.2 and NetBSD 1.3.2 and earlier releases, where the at command fails to properly validate file paths when processing files through the -f argument. The at program is designed to schedule commands for later execution, typically used for batch processing and automated tasks in Unix environments. When a local user submits a file to at using the -f flag, the system processes this file and generates error messages that are then sent to the user via email. This seemingly innocuous functionality becomes exploitable when the at program fails to properly sanitize input parameters, allowing an attacker to manipulate the file path argument in a way that bypasses normal access controls and reveals contents of arbitrary files on the system. The vulnerability stems from inadequate input validation and improper handling of file access permissions within the at command implementation.
The technical flaw manifests through the improper interaction between the at program's file processing mechanism and the email notification system. When the at command processes a file specified with the -f argument, it creates error messages that contain information about the file processing attempt. These error messages are automatically routed to the user's email address, which means that any information contained within the file being processed gets inadvertently exposed to the user. The vulnerability specifically exploits the fact that when at attempts to read or process files that are not properly validated, it generates error messages that include path information or file content, thereby enabling a local user to read portions of arbitrary files that would normally be protected by standard file permissions. This represents a classic case of information disclosure through improper error handling and insufficient input sanitization, where the system's attempt to provide diagnostic information inadvertently leaks sensitive data. The flaw aligns with CWE-200, which covers "Information Exposure Through Output Error Messages" and reflects a fundamental weakness in how the system handles error reporting for file operations.
The operational impact of this vulnerability is substantial for systems running affected versions of IRIX and NetBSD, as it allows local users to bypass normal file access controls and potentially access sensitive information. Attackers can leverage this vulnerability to read system configuration files, password files, application data, or any other files that are accessible to the at program's execution context. The ability to read arbitrary file contents represents a serious security risk, as it could expose system credentials, application secrets, or other confidential data that should remain protected. Since the vulnerability is local in nature, it requires physical or network access to the system but does not require special privileges to exploit. The impact extends beyond simple information disclosure, as the vulnerability could enable further attacks by providing attackers with insights into system structure and configuration. The attack vector is particularly concerning because it leverages legitimate system functionality, making it harder to detect and defend against, and the error messages could potentially reveal information about the system's internal state and file structure. This vulnerability also demonstrates the importance of proper input validation and the potential security implications of error handling mechanisms in system utilities.
Mitigation strategies for this vulnerability should focus on both immediate remediation and long-term architectural improvements. The most direct solution involves updating to patched versions of IRIX and NetBSD where the at program properly validates file paths and sanitizes error messages before sending them via email. System administrators should also implement proper access controls and monitoring for the at program, including limiting which users can execute at commands and monitoring for unusual file access patterns. The vulnerability highlights the need for comprehensive input validation in system utilities and proper error handling that does not expose internal system information. Organizations should consider implementing additional security controls such as file permission reviews, regular security audits of system utilities, and monitoring for unauthorized access attempts. From a defense-in-depth perspective, implementing network segmentation and access control lists can limit the potential impact of such vulnerabilities. The vulnerability also underscores the importance of following security best practices outlined in standards such as the NIST Cybersecurity Framework and the MITRE ATT&CK framework, particularly in areas related to privilege management and information protection. Regular security assessments and vulnerability management processes should include review of system utilities and their error handling mechanisms to prevent similar issues from occurring in other components of the system.