CVE-2008-4982 in rkhunter
Summary
by MITRE
rkhunter in rkhunter 1.3.2 allows local users to overwrite arbitrary files via a symlink attack on the /tmp/rkhunter-debug temporary file. NOTE: this is probably a different vulnerability than CVE-2005-1270.
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Analysis
by VulDB Data Team • 10/14/2018
The vulnerability identified as CVE-2008-4982 affects rkhunter version 1.3.2, a widely used rootkit detection tool designed to identify potential security threats on unix-like systems. This particular flaw represents a classic symlink attack scenario that exploits insecure temporary file handling practices within the software's operational environment. The vulnerability specifically targets the /tmp/rkhunter-debug temporary file location, which serves as a critical component in the tool's debugging and logging functionality during system scans. When rkhunter executes with elevated privileges, it creates temporary files in the /tmp directory without proper security measures to prevent symbolic link attacks. This insecure approach to temporary file management creates a pathway for local attackers to manipulate the tool's behavior through malicious symlink creation, potentially leading to arbitrary file overwrite operations.
The technical implementation of this vulnerability stems from the software's failure to validate the existence and ownership of temporary files before writing to them. During normal operation, rkhunter creates the /tmp/rkhunter-debug file to store debugging information and scan results. However, when a local attacker can manipulate the symbolic link structure in the /tmp directory, they can redirect the tool's write operations to arbitrary locations on the filesystem. This occurs because the application does not check whether the temporary file is a legitimate file or a symbolic link pointing elsewhere. The attacker can create a symbolic link named /tmp/rkhunter-debug that points to a critical system file such as /etc/passwd or /etc/shadow, allowing them to overwrite these sensitive files with arbitrary content. This flaw directly maps to CWE-377: Insecure Temporary File and CWE-378: Creation of Temporary File With Insecure Permissions, both of which are well-documented in the Common Weakness Enumeration catalog. The vulnerability is particularly concerning because it operates at the privilege level of the rkhunter process, which typically runs with elevated permissions to perform comprehensive system scans.
The operational impact of this vulnerability extends beyond simple file overwrites and represents a significant threat to system integrity and security posture. Local attackers with minimal privileges can leverage this flaw to escalate their access level within the system, potentially compromising the confidentiality, integrity, and availability of critical system resources. When rkhunter executes in a compromised environment, the malicious symlink attack can lead to persistent backdoors, credential theft, or complete system compromise. The vulnerability's exploitation requires local access but does not necessitate network connectivity, making it particularly dangerous in environments where physical or local access is possible. Security professionals should note that this vulnerability is classified under the MITRE ATT&CK framework as part of the privilege escalation techniques, specifically mapping to T1068: Exploitation for Privilege Escalation and T1548.1: Abuse of sudo. The attack vector involves the manipulation of temporary files, which is a common technique in Unix-based systems where insecure temporary file handling is prevalent.
Mitigation strategies for CVE-2008-4982 should focus on immediate remediation and long-term security hardening measures. The most effective immediate solution involves updating to a patched version of rkhunter that implements secure temporary file creation practices, specifically those that use atomic file creation methods and proper permission checks. System administrators should also implement proper file system permissions and ensure that the /tmp directory is mounted with the no_symlink option to prevent symbolic link attacks. Additionally, the application should be configured to create temporary files in directories with restricted permissions or use the mkstemp() function instead of relying on simple file creation methods. Organizations should conduct comprehensive security audits to identify other applications that may be vulnerable to similar temporary file handling issues, as this pattern is common in legacy software. Regular security monitoring and log analysis should include detection of suspicious symbolic link creation patterns in temporary directories. The remediation process should also involve implementing proper privilege separation and ensuring that security tools are not run with unnecessary elevated privileges. Long-term security measures should include regular vulnerability assessments, security code reviews, and adherence to secure coding practices that prevent similar issues from occurring in other software components.