CVE-2000-0829 in Linux
Summary
by MITRE
The tmpwatch utility in Red Hat Linux forks a new process for each directory level, which allows local users to cause a denial of service by creating deeply nested directories in /tmp or /var/tmp/.
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Analysis
by VulDB Data Team • 11/09/2024
The CVE-2000-0829 vulnerability represents a classic denial of service flaw in Unix-like systems that demonstrates the critical importance of process management and resource allocation in system utilities. This vulnerability specifically affects the tmpwatch utility distributed with Red Hat Linux, which is designed to automatically remove temporary files that have not been accessed for a specified period. The utility operates by recursively traversing directory structures to identify and delete stale temporary files, a common administrative task in Unix environments where temporary storage areas like /tmp and /var/tmp accumulate files over time.
The technical flaw in tmpwatch stems from its implementation approach where the utility creates a new process for each directory level it encounters during its traversal. This design choice, while functional for normal directory structures, becomes catastrophic when confronted with deeply nested directory hierarchies. When local users create numerous nested directories within the temporary storage areas, each directory level triggers a new fork operation that spawns a separate process. The process creation overhead accumulates exponentially with each additional nesting level, leading to resource exhaustion and ultimately system instability.
This vulnerability operates under the broader category of resource exhaustion attacks and falls under the CWE-400 category of Uncontrolled Resource Consumption. The operational impact of CVE-2000-0829 extends beyond simple denial of service as it can effectively cripple system administration functions and potentially affect other processes that depend on system resources. The attack vector requires local user access but does not require elevated privileges, making it particularly concerning for multi-user systems where unauthorized users could exploit this weakness to disrupt system operations. The vulnerability demonstrates how seemingly benign administrative utilities can become attack vectors when their process management strategies do not account for malicious input patterns.
The implications of this vulnerability align with ATT&CK technique T1499.004 which covers "Utilities: File Deletion" and highlights how legitimate system utilities can be weaponized for denial of service attacks. Organizations running affected versions of Red Hat Linux would experience degraded system performance, potential system crashes, and administrative difficulties as the system becomes overwhelmed with process creation. The attack scenario typically involves creating deeply nested directory structures that can be achieved through simple shell commands or scripting, making the exploit accessible to users with minimal technical expertise.
Mitigation strategies for CVE-2000-0829 primarily focus on updating to patched versions of the tmpwatch utility or implementing alternative temporary file management approaches. System administrators should ensure that all Red Hat Linux systems are updated to versions containing the fix that addresses the excessive process creation behavior. Additionally, implementing directory nesting limits or monitoring temporary storage areas for unusual directory structures can serve as defensive measures. The vulnerability also underscores the importance of proper input validation and resource management in system utilities, as well as the necessity of conducting security reviews of administrative tools that perform recursive operations. Organizations should consider implementing automated monitoring systems to detect unusual process creation patterns that might indicate exploitation attempts. The fix typically involves modifying the tmpwatch utility to use iterative approaches instead of recursive forking, or implementing process limits that prevent excessive resource consumption during directory traversal operations.