CVE-2009-4193 in Merkaartor
Summary
by MITRE
Merkaartor 0.14 allows local users to append data to arbitrary files via a symlink attack on the /tmp/merkaartor.log temporary file.
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Analysis
by VulDB Data Team • 08/28/2021
The vulnerability identified as CVE-2009-4193 affects Merkaartor version 0.14, a desktop mapping application designed for editing OpenStreetMap data. This issue represents a classic symlink attack scenario that exploits improper handling of temporary files during the application's operation. The flaw specifically manifests when Merkaartor creates or modifies log files in the /tmp directory without adequate security measures to prevent symbolic link manipulation by local attackers. The vulnerability falls under the category of insecure temporary file handling, which is a well-documented weakness in software security practices.
The technical implementation of this vulnerability stems from Merkaartor's failure to properly validate or secure its temporary file creation process. When the application attempts to write to /tmp/merkaartor.log, it does not verify whether the target path is a legitimate file or a symbolic link pointing to another location. An attacker with local access can create a symbolic link at the expected location that points to a critical system file or a file owned by a privileged user. When Merkaartor subsequently writes data to what it believes is its log file, it actually appends data to the target of the symbolic link, potentially corrupting system files or gaining unauthorized write access to protected locations. This type of attack leverages the fundamental principle that temporary files created without proper atomicity or security checks can be manipulated by malicious users.
The operational impact of this vulnerability extends beyond simple data corruption, as it provides attackers with a means to escalate privileges or manipulate system resources. Local attackers can exploit this weakness to inject malicious content into files they do not normally have write access to, potentially compromising system integrity and confidentiality. The vulnerability is particularly concerning because it does not require network access or complex exploitation techniques, making it readily available to any user with local system access. The attack vector aligns with attack techniques described in the MITRE ATT&CK framework under T1059 for executing malicious code and T1074 for data manipulation, though it specifically targets the initial compromise phase through insecure file handling rather than post-compromise activities.
Mitigation strategies for this vulnerability involve implementing proper temporary file handling practices that are consistent with industry security standards. The most effective approach requires Merkaartor to create temporary files with secure permissions and to verify that the target path is not a symbolic link before writing to it. This aligns with CWE-377, which specifically addresses insecure temporary file creation practices. Additionally, the application should utilize atomic file operations or create temporary files in directories with restricted permissions, such as those with the sticky bit set or in locations specifically designed for temporary file storage. System administrators should also consider implementing file system monitoring to detect unusual symbolic link creation patterns in temporary directories, while the software development team should review all temporary file operations to ensure they follow secure coding practices that prevent similar vulnerabilities from manifesting in future releases.
The vulnerability demonstrates how seemingly minor implementation oversights in file handling can create significant security risks in desktop applications. It highlights the importance of following secure coding guidelines and the necessity of thorough security testing, particularly for applications that operate in multi-user environments where local privilege escalation attacks are a real concern. Organizations should prioritize updating to patched versions of Merkaartor and implementing monitoring solutions to detect potential exploitation attempts, while developers should incorporate proper temporary file handling as a standard practice in their security development lifecycle processes.