CVE-2002-1193 in tkmail
Summary
by MITRE
tkmail before 4.0beta9-8.1 allows local users to create or overwrite files as users via a symlink attack on temporary files.
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Analysis
by VulDB Data Team • 06/30/2024
The vulnerability described in CVE-2002-1193 affects tkmail versions prior to 4.0beta9-8.1 and represents a classic file system race condition that enables local privilege escalation through symbolic link manipulation. This issue arises from improper handling of temporary files during the mail processing operations within the tkmail application. The flaw allows malicious local users to exploit the application's temporary file creation mechanism by creating symbolic links that point to sensitive system files or directories, thereby enabling them to write data to arbitrary locations with the privileges of other users. The vulnerability specifically targets the application's failure to properly validate or secure temporary file creation processes, creating an exploitable condition where the attacker can manipulate the file system state between the time a temporary file is checked for existence and the time it is actually used by the application.
The technical implementation of this vulnerability follows the pattern of a time-of-check to time-of-use race condition, where the application checks for the existence of a temporary file and then proceeds to use it without revalidating the file's integrity or ownership. This creates a window of opportunity for attackers to substitute the expected temporary file with a symbolic link pointing to a target file. When the application subsequently writes to what it believes is a temporary file, it actually writes to the target file specified by the symbolic link, potentially overwriting critical system files or creating malicious files with elevated privileges. This type of vulnerability is categorized under CWE-367, which specifically addresses Time-of-Check to Time-of-Use race conditions, and represents a common attack vector in Unix-like systems where file operations are not properly synchronized or secured against manipulation.
The operational impact of this vulnerability extends beyond simple file creation or modification, as it can potentially enable privilege escalation attacks within the local system. An attacker who successfully exploits this vulnerability can create files with the privileges of other users, potentially allowing them to modify system configuration files, create backdoor accounts, or overwrite critical binaries. The attack is particularly concerning because it requires only local access to the system, making it accessible through various attack vectors including compromised user accounts, shared system access, or other local privilege escalation techniques. The vulnerability affects the integrity and confidentiality of the system by allowing unauthorized modification of files that should be protected from arbitrary user manipulation, potentially leading to persistent access or system compromise.
Mitigation strategies for this vulnerability involve implementing proper temporary file handling mechanisms that prevent the exploitation of race conditions. The most effective approach is to use secure temporary file creation methods such as creating files with restrictive permissions and using atomic operations that prevent symbolic link manipulation. The application should ensure that temporary files are created with unique names that cannot be predicted or manipulated by attackers, and that proper file ownership and permission checks are performed throughout the file creation and usage lifecycle. System administrators should upgrade to tkmail version 4.0beta9-8.1 or later, which contains the necessary patches to address this vulnerability. Additionally, implementing proper file system permissions, using restricted user accounts for running the application, and monitoring for unauthorized file system changes can help detect and prevent exploitation attempts. This vulnerability highlights the importance of following secure coding practices as outlined in the OWASP Secure Coding Practices and aligns with ATT&CK technique T1068, which covers the exploitation of local privilege escalation vulnerabilities through file system manipulation.