CVE-2008-4954 in fml
Summary
by MITRE
mead.pl in fml 4.0.3 allows local users to overwrite arbitrary files via a symlink attack on the /tmp/debugbuf temporary file.
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Analysis
by VulDB Data Team • 10/13/2018
The vulnerability identified as CVE-2008-4954 resides within the mead.pl script component of the fml 4.0.3 software suite, presenting a significant local privilege escalation risk through a carefully crafted symbolic link attack. This flaw specifically targets the temporary file handling mechanism used by the application during debugging operations, creating an exploitable condition that allows unauthorized users to manipulate system files through indirect means. The vulnerability manifests when the application creates a temporary file named debugbuf in the /tmp directory without proper security checks, making it susceptible to symlink-based attacks that can redirect file operations to arbitrary locations within the filesystem.
The technical implementation of this vulnerability follows a classic race condition pattern where the application first checks for the existence of a temporary file and then creates it, leaving a window where a malicious user can insert a symbolic link that points to a target file of their choice. This type of vulnerability falls under CWE-367, which specifically addresses Time-of-Check to Time-of-Use (TOCTOU) race conditions that can lead to privilege escalation and unauthorized file access. The flaw demonstrates poor security hygiene in temporary file creation practices, where the application does not employ secure methods such as creating files with exclusive access permissions or using proper atomic file creation mechanisms that prevent symbolic link manipulation during the file creation process.
From an operational perspective, this vulnerability enables local attackers to overwrite critical system files, configuration data, or even executable binaries with malicious content, potentially leading to complete system compromise. The attack vector is particularly concerning because it requires minimal privileges to execute and can be leveraged to escalate privileges or maintain persistent access to the compromised system. Security researchers have noted that such vulnerabilities are often exploited in conjunction with other attack vectors, where the initial compromise through file overwriting leads to further privilege escalation or lateral movement within the network infrastructure. The impact extends beyond simple file corruption, as attackers can use this technique to modify system binaries, create backdoors, or manipulate system logs to cover their tracks.
The mitigation strategies for CVE-2008-4954 require immediate implementation of proper temporary file handling practices that align with security best practices outlined in various industry standards and frameworks. Organizations should implement secure file creation mechanisms that utilize atomic operations or create temporary files with restrictive permissions that prevent symbolic link manipulation. The solution involves modifying the application code to either use secure temporary file creation functions that prevent race conditions or to validate the target of symbolic links before performing file operations. This vulnerability directly relates to ATT&CK technique T1059.007, which covers the use of scripting languages to execute malicious code, and T1548.001, which addresses privilege escalation through abuse of system permissions. System administrators should also implement proper monitoring of the /tmp directory for suspicious symbolic link creation patterns and ensure that all system components are updated to versions that address this specific vulnerability through secure coding practices and proper input validation.