CVE-2008-4946 in convirt
Summary
by MITRE
convirt 0.8.2 allows local users to overwrite arbitrary files via a symlink attack on the /tmp/set_output temporary file, related to the (1) _template_/provision.sh, (2) Linux_CD_Install/provision.sh, (3) Fedora_PV_Install/provision.sh, (4) CentOS_PV_Install/provision.sh, (5) common/provision.sh, (6) example/provision.sh, and (7) Windows_CD_Install/provision.sh scripts in image_store/.
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Analysis
by VulDB Data Team • 10/13/2018
The vulnerability described in CVE-2008-4946 represents a critical path traversal and symbolic link attack flaw within the convirt virtualization management platform version 0.8.2. This issue stems from improper handling of temporary files during the provisioning process, specifically targeting the /tmp/set_output file location which serves as a critical temporary storage point for system operations. The vulnerability affects multiple provisioning scripts across different operating system templates, indicating a systemic flaw in the temporary file management approach rather than an isolated incident. The attack vector exploits the predictable naming of temporary files and the lack of proper security checks when creating or accessing these temporary resources, allowing local attackers to manipulate the system's file operations through carefully crafted symbolic link attacks.
The technical implementation of this vulnerability involves the exploitation of insecure temporary file creation practices where the provisioning scripts do not adequately validate or secure their temporary file operations. When these scripts execute, they create or reference the /tmp/set_output file without sufficient safeguards against symbolic link manipulation. Attackers can create malicious symbolic links in the /tmp directory that point to sensitive system files, effectively allowing them to overwrite critical files with arbitrary content. This type of attack falls under the category of symlink-based attacks that leverage predictable temporary file names and insufficient input validation. The vulnerability is particularly dangerous because it operates at the system level where temporary files are commonly used for inter-process communication and data exchange during complex operations.
The operational impact of this vulnerability extends beyond simple file overwrites to potentially compromise the entire virtualization management platform. Since these provisioning scripts are responsible for system configuration and virtual machine deployment, successful exploitation could lead to privilege escalation, system compromise, or complete platform takeover. The attack requires local system access, but once successful, it can provide attackers with the ability to modify critical system files, inject malicious code, or disrupt normal platform operations. The affected scripts cover multiple virtualization environments including Linux distributions and Windows installations, making the impact widespread across different deployment scenarios. This vulnerability demonstrates a fundamental lack of proper temporary file handling security practices that should be implemented in all system components handling user or system-generated temporary data.
Mitigation strategies for this vulnerability should focus on implementing secure temporary file creation practices and eliminating predictable file naming patterns. The most effective approach involves using secure temporary file creation functions that prevent symbolic link attacks, such as those provided by the mkstemp family of functions in unix-like systems. Additionally, proper file permissions and ownership checks should be implemented to ensure that temporary files are created with restrictive access rights and that symbolic links are not followed during file operations. The convirt platform should also implement input validation and sanitization for all temporary file paths, ensuring that absolute paths are used and that symbolic links are explicitly checked and rejected. This vulnerability aligns with CWE-377: Insecure Temporary File and CWE-378: Poor Permissions for Temporary Files, both of which are commonly exploited in privilege escalation scenarios. From an ATT&CK perspective, this vulnerability maps to T1059.001 for command and scripting interpreter and T1548.002 for abuse of sudo privileges, as the compromised temporary files could be leveraged to escalate local privileges or gain unauthorized access to system resources. System administrators should also implement monitoring and alerting for unusual file system activity in temporary directories and consider implementing mandatory access controls to limit the impact of such vulnerabilities.