CVE-2008-5372 in sdm-terminal
Summary
by MITRE
sdm-login in sdm-terminal 0.4.0b allows local users to overwrite arbitrary files via a symlink attack on the /tmp/sdm.autologin.once temporary file.
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Analysis
by VulDB Data Team • 10/21/2018
The vulnerability identified as CVE-2008-5372 represents a critical file system permission flaw within the sdm-terminal 0.4.0b software package, specifically affecting the sdm-login component. This issue arises from improper handling of temporary files during the authentication process, creating a path for local privilege escalation through symbolic link manipulation. The vulnerability exists because the application creates temporary files without adequate security checks, leaving the system exposed to malicious file overwrites by local users who can exploit the predictable temporary file location.
The technical implementation of this flaw involves the creation of a temporary file at /tmp/sdm.autologin.once which lacks proper security measures to prevent symbolic link attacks. When the sdm-login component processes authentication requests, it generates this temporary file without validating whether the target path is a symbolic link or if the file already exists. This behavior creates a race condition scenario where a local attacker can establish a symbolic link pointing to a critical system file before the legitimate application creates the temporary file, resulting in the attacker's controlled data being written to the target location instead of the intended temporary file. This vulnerability directly maps to CWE-377: Insecure Temporary File and CWE-378: Creation of Temporary File With Insecure Permissions, both of which are well-documented weaknesses in software security practices.
The operational impact of this vulnerability extends beyond simple file overwrites, as it provides local users with a potential pathway to escalate privileges within the system. An attacker could leverage this vulnerability to overwrite system configuration files, authentication databases, or even critical binaries, potentially leading to complete system compromise. The attack requires local access and minimal privileges to execute, making it particularly dangerous in multi-user environments where users might have legitimate access to the system but should not possess the ability to modify critical system files. This vulnerability essentially undermines the principle of least privilege by allowing unauthorized file modifications through legitimate application processes.
Mitigation strategies for CVE-2008-5372 should focus on implementing proper temporary file handling mechanisms that address the core security flaw. Organizations should ensure that temporary files are created with secure permissions and are not susceptible to symbolic link attacks by using functions like mkstemp() instead of creating files with predictable names. The application should validate that temporary files are not symbolic links before proceeding with file operations and should implement proper file ownership checks. Additionally, system administrators should consider implementing mandatory access controls through SELinux or AppArmor policies to limit the impact of such vulnerabilities. The remediation aligns with ATT&CK technique T1059.001 for executing commands through system binaries and T1078 for valid accounts, as the vulnerability exploits legitimate system components to achieve unauthorized file modifications. Regular security audits and penetration testing should be conducted to identify similar insecure temporary file handling patterns across the system, ensuring comprehensive protection against similar privilege escalation vulnerabilities.