CVE-2006-1753 in Linux
Summary
by MITRE
A cron job in fcheck before 2.7.59 allows local users to overwrite arbitrary files via a symlink attack on a temporary file.
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Analysis
by VulDB Data Team • 07/21/2019
The vulnerability identified as CVE-2006-1753 affects the fcheck utility version 2.7.59 and earlier, representing a significant local privilege escalation risk through insecure temporary file handling. This issue specifically manifests within the cron job execution context of fcheck, where the utility creates temporary files during its operation. The flaw stems from improper handling of symbolic links within the temporary file creation process, allowing local attackers to manipulate the system by creating malicious symbolic links that point to arbitrary files. The vulnerability is categorized under CWE-377 as insecure temporary file creation, which directly relates to the improper use of temporary files that can be exploited by attackers with local access. When a cron job executes fcheck, it processes a temporary file that is susceptible to symlink attacks, enabling an attacker to redirect file operations to sensitive system files or configuration files that the utility may modify. This type of attack falls under the ATT&CK technique T1059.007 for command and scripting interpreter and T1068 for exploit for privilege escalation.
The technical exploitation of this vulnerability requires an attacker to have local system access and the ability to create symbolic links in the directory where fcheck creates its temporary files. During normal operation, fcheck creates a temporary file that is later processed by the cron job, but due to the lack of proper validation or secure temporary file creation methods, an attacker can place a symbolic link in the same directory with the same name as the temporary file. When the cron job executes, it follows the symbolic link and writes data to the target file specified by the link, potentially overwriting critical system files or configuration data. The flaw essentially creates a race condition between the creation of the temporary file and the subsequent file operations, where the attacker can manipulate the file system to redirect the write operations to unintended targets. This vulnerability demonstrates poor security practices in temporary file handling and represents a classic example of a race condition attack vector.
The operational impact of this vulnerability is substantial for systems that rely on fcheck for file integrity monitoring, particularly in environments where local users may have varying levels of access. Attackers could potentially overwrite critical system files such as configuration files, binaries, or log files, leading to system instability, data corruption, or complete system compromise. The vulnerability affects systems where fcheck is configured to run as a cron job, which is common in security monitoring and compliance environments. When exploited, this vulnerability can enable attackers to modify system configurations or replace critical binaries, potentially providing them with persistent access or the ability to escalate privileges beyond their initial local access. The attack vector is particularly concerning because it requires minimal privileges to exploit and can be automated through the existing cron job infrastructure, making it a preferred target for attackers seeking to establish persistent access or manipulate system integrity monitoring mechanisms. Organizations using affected versions of fcheck should prioritize patching and implement monitoring for unusual file modification patterns in directories where temporary files are created. The vulnerability also highlights the importance of secure coding practices for utilities that handle temporary files, emphasizing the need for atomic file creation, proper file permissions, and validation of file paths to prevent symlink-based attacks that can compromise system integrity and availability.