CVE-2008-4986 in wims
Summary
by MITRE
wims 3.62 allows local users to overwrite arbitrary files via a symlink attack on (a) /tmp/env#####, (b) /tmp/sed#####, and (c) /tmp/referer-home.log temporary files, related to the (1) coqweb and (2) account.sh scripts.
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Analysis
by VulDB Data Team • 10/14/2018
The vulnerability identified as CVE-2008-4986 affects wims version 3.62, a web-based interactive mathematics software system designed for online education and assessment. This weakness represents a classic symlink attack scenario that exploits predictable temporary file names to enable unauthorized file overwrites. The vulnerability specifically targets three temporary files located in the /tmp directory: /tmp/env#####, /tmp/sed#####, and /tmp/referer-home.log. These files are created with predictable naming patterns that include sequential numbering, making them susceptible to exploitation by local attackers who can manipulate the system's temporary file creation process.
The technical flaw stems from the insecure handling of temporary files within the coqweb and account.sh scripts that are part of the wims software suite. When these scripts execute, they create temporary files with predictable names in the /tmp directory without proper security measures to prevent symbolic link attacks. Attackers can create symbolic links with the same names as the expected temporary files before the vulnerable scripts run, causing the scripts to write data to attacker-controlled locations instead of the intended temporary files. This behavior directly violates the principle of least privilege and demonstrates poor file handling practices that are commonly classified as CWE-377: Insecure Temporary Files.
The operational impact of this vulnerability is significant for local attackers who can leverage it to overwrite arbitrary files on the system with the privileges of the user running the vulnerable scripts. Since the temporary files are created in the /tmp directory, which is typically world-writable, attackers can easily establish symbolic links that redirect the script's output to sensitive system files or configuration files. This could lead to privilege escalation, data corruption, or even complete system compromise depending on which files are overwritten. The vulnerability affects the integrity of the system and can be exploited to maintain persistent access or hide malicious activities within the wims environment.
Security practitioners should implement multiple layers of defense to mitigate this vulnerability. The most effective immediate solution involves modifying the vulnerable scripts to use secure temporary file creation methods such as mkstemp() or similar functions that create files with unpredictable names and proper permissions. Additionally, administrators should ensure that the /tmp directory has appropriate permissions and consider mounting it with the no_symlinks option to prevent symbolic link creation. This vulnerability aligns with ATT&CK technique T1059.007 for executing commands through scripts and T1548.001 for privilege escalation. System hardening measures including regular security audits, proper file permissions, and monitoring for suspicious file creation patterns should be implemented to prevent exploitation of similar vulnerabilities in other software components. The vulnerability also highlights the importance of following secure coding practices and proper input validation as outlined in OWASP Top 10 and NIST guidelines for secure software development.