CVE-2008-5137 in tkman
Summary
by MITRE
tkman in tkman 2.2 allows local users to overwrite arbitrary files via a symlink attack on a (1) /tmp/tkman##### or (2) /tmp/ll temporary file.
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Analysis
by VulDB Data Team • 08/03/2021
The vulnerability identified as CVE-2008-5137 affects tkman version 2.2 and represents a classic insecure temporary file creation flaw that enables local privilege escalation through symbolic link attacks. This vulnerability resides in the temporary file handling mechanism of the tkman application, which is commonly used for managing and displaying graphical user interface elements in various desktop environments. The flaw manifests when the application creates temporary files in the /tmp directory without proper security checks, making it susceptible to race conditions and symlink attacks that can be exploited by local users to gain elevated privileges or execute arbitrary code with the privileges of the target process.
The technical implementation of this vulnerability stems from the application's failure to validate the existence and ownership of temporary files before writing to them. When tkman creates temporary files using patterns such as /tmp/tkman##### or /tmp/ll, it does not perform adequate checks to ensure these files do not already exist as symbolic links pointing to sensitive system locations. This insecure practice creates a window of opportunity where a malicious local user can pre-create symbolic links with the same names as the temporary files that tkman intends to create, effectively redirecting the application's file operations to arbitrary locations on the filesystem. The vulnerability is particularly dangerous because it can be exploited to overwrite critical system files, configuration files, or even setuid binaries, potentially leading to privilege escalation or complete system compromise.
The operational impact of this vulnerability extends beyond simple file overwriting capabilities and represents a significant threat to system integrity and security. Attackers can leverage this weakness to overwrite files in system directories with predictable names, potentially gaining access to administrative privileges or corrupting system functionality. The vulnerability affects systems where tkman is installed and executed with elevated privileges, making it particularly concerning for multi-user environments or systems where the application runs with root privileges. This type of vulnerability is classified under CWE-377: Insecure Temporary Files and is closely related to the broader category of race condition exploits that are frequently targeted in privilege escalation attacks. The attack vector aligns with techniques documented in the MITRE ATT&CK framework under T1068: Exploitation for Privilege Escalation, specifically targeting local system processes that create temporary files without proper security controls.
Mitigation strategies for CVE-2008-5137 require immediate attention and should include updating to a patched version of tkman that implements secure temporary file creation practices. System administrators should ensure that all instances of tkman are updated to versions that properly handle temporary file creation by using secure methods such as creating temporary files with unique, unpredictable names and verifying file ownership before writing to them. The recommended approach involves implementing proper file descriptor management and using system calls that guarantee atomic file creation, such as the O_EXCL flag in open() system calls. Additionally, organizations should conduct comprehensive system audits to identify all installations of affected software and ensure that temporary file directories have appropriate permissions to prevent unauthorized symbolic link creation. System hardening measures should include restricting the ability to create symbolic links in critical temporary directories and implementing proper file system permissions that prevent local users from overwriting system-critical files through such attack vectors. The vulnerability demonstrates the importance of following secure coding practices and adhering to the principle of least privilege when handling temporary file operations in applications that may be executed with elevated privileges.