CVE-2008-4988 in xcal
Summary
by MITRE
pscal in xcal 4.1 allows local users to overwrite arbitrary files via a symlink attack on a /tmp/pscal##### temporary file.
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Analysis
by VulDB Data Team • 10/14/2018
The vulnerability identified as CVE-2008-4988 affects the pscal utility within the xcal 4.1 software suite, presenting a significant security risk through improper temporary file handling. This flaw enables local attackers to perform symlink attacks against temporary files created in the /tmp directory, specifically targeting files named with the pattern /tmp/pscal##### where the hash symbols represent random digits. The issue stems from the application's failure to properly validate or secure temporary file creation processes, creating an exploitable race condition that can be leveraged by malicious users with local access.
The technical implementation of this vulnerability involves the creation of temporary files without adequate security measures to prevent symbolic link manipulation. When pscal executes, it generates temporary files in the /tmp directory using predictable naming conventions that can be exploited through a time-of-check to time-of-use race condition. An attacker can create a symbolic link with the same name as the temporary file that pscal will later create, effectively redirecting the application's file operations to arbitrary locations on the filesystem. This allows the attacker to overwrite or modify files with the privileges of the user running the pscal utility, potentially leading to privilege escalation or data corruption.
From an operational perspective, this vulnerability poses a serious threat to system integrity and security, particularly in multi-user environments where local access might be obtained through various means such as legitimate user accounts or compromised credentials. The impact extends beyond simple file overwrites, as attackers can potentially target critical system files, configuration data, or files belonging to other users. The vulnerability is classified under CWE-377 as "Insecure Temporary File" and aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: PowerShell" and T1078.004 for "Valid Accounts: Default Accounts" when considering the potential for privilege escalation through file modification attacks. The attack vector requires local system access, making it particularly concerning in environments where users might have limited privileges but could potentially escalate their access through such vulnerabilities.
Mitigation strategies for CVE-2008-4988 should focus on implementing proper temporary file handling practices that eliminate the race condition vulnerability. System administrators should ensure that temporary files are created with secure permissions and unique naming schemes that prevent symlink attacks. The recommended approach includes using secure temporary file creation functions that guarantee atomic file creation, implementing proper file access controls, and avoiding predictable naming patterns in temporary file generation. Additionally, the application should be updated to use more secure methods of temporary file management that prevent attackers from creating symbolic links in the target directory before the application creates its own temporary files. Organizations should also consider implementing monitoring for suspicious file creation patterns and ensure that the xcal software suite is updated to versions that address this specific vulnerability through proper temporary file handling mechanisms that align with security best practices established in standards such as NIST SP 800-128 and ISO/IEC 27001.