CVE-2002-1963 in Linux
Summary
by MITRE
Linux kernel 2.4.1 through 2.4.19 sets root s NR_RESERVED_FILES limit to 10 files, which allows local users to cause a denial of service (resource exhaustion) by opening 10 setuid binaries.
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Analysis
by VulDB Data Team • 07/07/2024
The vulnerability described in CVE-2002-1963 represents a critical resource management flaw within the Linux kernel version 2.4.1 through 2.4.19 that exposes systems to denial of service attacks. This issue stems from the kernel's handling of the root user's reserved file descriptor limit, specifically setting the NR_RESERVED_FILES parameter to only ten files. The design flaw creates a scenario where a local attacker can exploit this limitation to exhaust available file descriptors and effectively disrupt system operations.
The technical implementation of this vulnerability occurs through the manipulation of file descriptor limits within the kernel's resource management framework. When the root user attempts to open setuid binaries, the kernel's reserved file descriptor allocation mechanism becomes constrained by the artificially low limit of ten files. This constraint becomes exploitable when an attacker repeatedly opens setuid binaries, each consuming one of the reserved file descriptors. As these descriptors are consumed, legitimate system processes that require file access may be unable to acquire new file descriptors, leading to cascading failures in system functionality.
The operational impact of this vulnerability extends beyond simple resource exhaustion, creating a potential pathway for broader system compromise. Local users can leverage this flaw to systematically consume available file descriptors, potentially causing critical system services to fail or become unresponsive. The attack vector is particularly dangerous because it requires no special privileges beyond local access, making it an attractive target for malicious actors who have gained initial system foothold. The vulnerability directly impacts the Linux kernel's file descriptor management system and can be categorized under CWE-474, which addresses the use of insecure functions that could lead to resource exhaustion.
The exploitation of this vulnerability aligns with several attack patterns documented in the MITRE ATT&CK framework, particularly those involving privilege escalation and denial of service. The attack demonstrates how seemingly minor kernel configuration parameters can create significant security implications when combined with local user access. From a defensive standpoint, this vulnerability highlights the importance of proper resource limit configuration and the need for comprehensive system hardening practices. The issue also reflects broader concerns about the balance between system security and resource availability, particularly in multi-user environments where root privileges are shared among multiple users.
Mitigation strategies for CVE-2002-1963 should focus on both immediate system patches and long-term configuration hardening. The most effective immediate solution involves upgrading to a kernel version beyond 2.4.19, where this specific vulnerability has been addressed through proper file descriptor limit management. System administrators should also implement proper monitoring of file descriptor usage and establish automated alerts when resource limits approach critical thresholds. Additionally, implementing process limits and file descriptor quotas can provide additional protection against similar resource exhaustion attacks. The vulnerability serves as a reminder of the critical importance of kernel security updates and the potential for seemingly minor configuration issues to create significant system stability problems.