CVE-2015-0858 in TarDiff
Summary
by MITRE
Cool Projects TarDiff allows local users to write to arbitrary files via a symlink attack on a pathname in a /tmp/tardiff-$$ temporary directory.
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Analysis
by VulDB Data Team • 07/29/2022
The vulnerability identified as CVE-2015-0858 affects the Cool Projects TarDiff utility, which is designed to compare tar archives and generate diff files. This flaw represents a classic race condition and symlink attack scenario that enables local attackers to manipulate file system operations within the temporary directory structure. The vulnerability stems from insufficient validation of temporary file paths and inadequate handling of symbolic links during file creation operations. Attackers can exploit this weakness by creating malicious symbolic links in the /tmp/tardiff-$$ directory before the utility processes them, thereby redirecting file writes to arbitrary locations on the system.
The technical implementation of this vulnerability involves the exploitation of a time-of-check to time-of-use (TOCTOU) race condition within the temporary directory handling mechanism. When TarDiff creates temporary files in the /tmp/tardiff-$$ directory, it first checks for the existence of certain paths and then performs file operations without revalidating the path integrity. This creates an opportunity for attackers to establish symbolic links that point to sensitive system files or directories, causing the utility to write data to unintended locations. The $$ in the temporary directory name represents process ID placeholders that are typically generated by the system, but the predictable nature of these temporary paths combined with the lack of proper atomic operations creates the attack vector.
From an operational perspective, this vulnerability poses significant risks to system integrity and security posture. Local users who can execute the TarDiff utility can leverage this flaw to overwrite critical system files, modify configuration data, or inject malicious content into sensitive locations. The impact extends beyond simple file corruption as attackers can potentially escalate privileges by targeting system binaries or configuration files that are written to during the utility's operation. The vulnerability is particularly concerning in multi-user environments where unprivileged users might gain access to temporary file creation capabilities that could be exploited for privilege escalation or data manipulation attacks.
The attack surface for this vulnerability aligns with several cybersecurity frameworks and threat modeling concepts. From a CWE perspective, this represents a weakness categorized under CWE-377: Insecure Temporary Files, which specifically addresses the risks associated with temporary file creation and manipulation. The vulnerability also maps to ATT&CK technique T1059.007 for execution through scripts and T1068 for local privilege escalation, as attackers can leverage the file write capabilities to modify system components. Security professionals should consider this vulnerability as part of broader privilege escalation attack vectors that exploit poorly managed temporary file operations. The remediation approach should focus on implementing atomic file creation mechanisms, proper temporary directory permissions, and validating file paths before any write operations occur.
Mitigation strategies for CVE-2015-0858 should include immediate patching of affected versions of Cool Projects TarDiff to address the race condition in temporary file handling. System administrators should implement proper temporary directory management by ensuring that temporary files are created with secure permissions and atomic operations that prevent symlink attacks. The use of secure temporary file creation functions such as mkstemp() instead of relying on predictable temporary directory names can significantly reduce the attack surface. Additionally, implementing proper file system permissions and access controls for temporary directories, combined with regular security auditing of file system operations, will help detect and prevent exploitation attempts. Organizations should also consider implementing process monitoring to detect unauthorized file creation or modification activities in temporary directories, particularly during execution of system utilities that handle temporary file operations.