CVE-1999-0836 in UnixWare
Summary
by MITRE
UnixWare uidadmin allows local users to modify arbitrary files via a symlink attack.
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Analysis
by VulDB Data Team • 12/25/2024
The vulnerability described in CVE-1999-0836 represents a classic privilege escalation flaw in the UnixWare operating system's uidadmin utility. This issue stems from improper handling of symbolic links during file operations, creating a path traversal vulnerability that allows local attackers to manipulate files they should not have access to. The uidadmin utility, designed for user identification and management tasks, fails to properly validate file paths when processing symbolic links, enabling malicious users to redirect file operations to arbitrary locations within the filesystem.
The technical root cause of this vulnerability aligns with CWE-367, which describes the dangerous use of symlink in security-critical contexts. When uidadmin processes file operations, it does not properly resolve symbolic links before performing file modifications, allowing attackers to create malicious symbolic links that point to sensitive system files. This flaw operates under the principle of time-of-check to time-of-use vulnerabilities where the utility checks file permissions at one point but modifies different files at another point in the execution cycle. The vulnerability specifically targets the file system's security model by exploiting the trust relationship between the utility and file operations.
From an operational impact perspective, this vulnerability enables local users to escalate their privileges and modify critical system files, potentially leading to complete system compromise. Attackers can leverage this flaw to overwrite system binaries, modify configuration files, or inject malicious code into the system. The attack vector requires local access but does not need network connectivity, making it particularly dangerous in multi-user environments where users might have legitimate access to the system but should not have the ability to modify protected files. This vulnerability directly impacts the integrity and confidentiality of the UnixWare system, as unauthorized modifications can alter system behavior and provide persistent access to attackers.
The mitigation strategies for this vulnerability should focus on proper input validation and secure file handling practices. System administrators should ensure that all file operations within uidadmin and similar utilities properly resolve symbolic links before processing, using mechanisms such as realpath() calls to normalize file paths. Additionally, implementing proper file permission checking and using secure coding practices that avoid unsafe symbolic link handling can prevent this class of vulnerability. According to ATT&CK framework, this vulnerability maps to T1068, which covers 'Local Privilege Escalation' through the exploitation of system utilities. Organizations should also consider implementing file integrity monitoring solutions and regular security audits to detect unauthorized modifications to critical system files that might result from such attacks. The fix typically involves updating the uidadmin utility to properly handle symbolic links and validate file operations before execution, ensuring that file paths are fully resolved and validated against expected locations before any modifications occur.