CVE-2008-5153 in Moodle
Summary
by MITRE
spell-check-logic.cgi in Moodle 1.8.2 allows local users to overwrite arbitrary files via a symlink attack on the (1) /tmp/spell-check-debug.log, (2) /tmp/spell-check-before, or (3) /tmp/spell-check-after temporary file.
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Analysis
by VulDB Data Team • 08/26/2019
The vulnerability identified as CVE-2008-5153 affects Moodle version 1.8.2 and resides in the spell-check-logic.cgi component. This represents a critical file system permission and symlink attack vulnerability that enables local attackers to manipulate arbitrary files on the system. The flaw specifically targets three temporary files located in the /tmp directory: spell-check-debug.log, spell-check-before, and spell-check-after. These temporary files are created with predictable names and locations, making them susceptible to symbolic link manipulation attacks. The vulnerability stems from insufficient validation of temporary file creation processes and inadequate permissions handling during spell checking operations.
The technical implementation of this vulnerability exploits the predictable naming scheme of temporary files and the lack of proper symlink detection mechanisms. When Moodle processes spell checking operations, it creates temporary files with fixed names in the /tmp directory without verifying whether these files are symbolic links. An attacker can create malicious symbolic links pointing to sensitive system files before the spell-check-logic.cgi script executes, allowing them to overwrite critical files with arbitrary content. This type of vulnerability falls under CWE-377, which addresses insecure temporary file handling, and specifically aligns with CWE-59, which covers symlink attacks. The attack vector requires local system access but can potentially escalate privileges or cause system instability through strategic file overwrites.
From an operational impact perspective, this vulnerability compromises the integrity and confidentiality of the Moodle installation and underlying system. Local attackers can leverage this flaw to overwrite critical system files, configuration data, or even system binaries, potentially leading to privilege escalation or complete system compromise. The temporary file manipulation allows attackers to inject malicious content into files that should remain protected, undermining the security posture of educational platforms that rely on Moodle for content management and user interaction. This vulnerability is particularly concerning in multi-user environments where multiple local accounts exist, as it provides a potential path for attackers to persist on systems or escalate privileges through strategic file overwrites.
Mitigation strategies for CVE-2008-5153 involve multiple layers of defensive measures including immediate patching of affected Moodle installations to versions that address the temporary file handling vulnerability. System administrators should implement proper file permissions and ownership controls for temporary directories, ensuring that temporary files are created with secure umask settings and appropriate access controls. The implementation of proper symlink detection mechanisms within the spell-check-logic.cgi script is essential to prevent attackers from creating malicious symbolic links before file operations occur. Additionally, system monitoring should be enhanced to detect unusual file creation patterns in temporary directories, and regular security audits should verify that temporary file handling processes follow secure coding practices. This vulnerability demonstrates the importance of following secure coding guidelines such as those outlined in the OWASP Secure Coding Practices and aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as attackers may leverage this vulnerability to execute malicious code through file overwrites. Organizations should also consider implementing mandatory access controls and regular vulnerability assessments to identify similar weaknesses in other applications and systems.