CVE-2002-0638 in Secure OS
Summary
by MITRE
setpwnam.c in the util-linux package, as included in Red Hat Linux 7.3 and earlier, and other operating systems, does not properly lock a temporary file when modifying /etc/passwd, which may allow local users to gain privileges via a complex race condition that uses an open file descriptor in utility programs such as chfn and chsh.
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Analysis
by VulDB Data Team • 10/24/2024
The vulnerability described in CVE-2002-0638 represents a critical race condition flaw in the util-linux package that affects multiple operating systems including Red Hat Linux 7.3 and earlier versions. This issue specifically resides in the setpwnam.c component which handles password file modifications through various utility programs. The core problem manifests when these programs attempt to modify the system's /etc/passwd file without proper file locking mechanisms, creating a window of opportunity for malicious exploitation.
The technical implementation of this vulnerability stems from improper handling of temporary files during the password modification process. When utility programs like chfn and chsh execute, they create temporary files to facilitate the modification of user account information in /etc/passwd. However, the absence of adequate file locking prevents concurrent access to these temporary files, allowing a local attacker to exploit a race condition where they can manipulate the temporary file contents before the legitimate modification process completes. This flaw operates at the system level and requires local access to exploit, making it particularly dangerous in environments where local user privileges are not properly restricted.
The operational impact of CVE-2002-0638 extends beyond simple privilege escalation to potentially enable full system compromise when combined with other attack vectors. Attackers can leverage this vulnerability to gain root access by manipulating the temporary file contents in such a way that their malicious modifications are seamlessly integrated into the /etc/passwd file. The race condition aspect means that the timing of file operations becomes crucial, allowing attackers to exploit the window between file creation and modification. This vulnerability directly maps to CWE-362, which describes race conditions in file operations, and aligns with ATT&CK technique T1068, which covers local privilege escalation through race conditions and file manipulation. The attack requires careful coordination of file descriptor management and process timing to successfully exploit the flaw.
Mitigation strategies for this vulnerability involve implementing proper file locking mechanisms during temporary file operations and ensuring atomic file modifications. System administrators should immediately apply security patches from their respective vendors, as this vulnerability was addressed through updates to the util-linux package that included proper file locking. Additional defensive measures include restricting access to utility programs that are vulnerable to this attack, implementing proper file system permissions, and monitoring for suspicious file access patterns in the /tmp directory. Organizations should also consider implementing mandatory access controls and regular security audits to detect potential exploitation attempts. The vulnerability demonstrates the critical importance of proper resource management in system utilities and highlights the need for comprehensive security testing of core system components that handle sensitive data modifications.