CVE-2001-0907 in Linux
Summary
by MITRE
Linux kernel 2.2.1 through 2.2.19, and 2.4.1 through 2.4.10, allows local users to cause a denial of service via a series of deeply nested symlinks, which causes the kernel to spend extra time when trying to access the link.
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Analysis
by VulDB Data Team • 09/22/2024
The vulnerability described in CVE-2001-0907 represents a classic denial of service flaw affecting multiple versions of the Linux kernel. This issue specifically targets kernel versions 2.2.1 through 2.2.19 and 2.4.1 through 2.4.10, where the kernel fails to properly handle deeply nested symbolic links. The flaw stems from inadequate recursion handling within the kernel's symbolic link resolution mechanism, creating a scenario where malicious users can exploit the system's path resolution capabilities to consume excessive computational resources.
The technical implementation of this vulnerability involves the creation of symbolic link chains that extend to considerable depths within the filesystem hierarchy. When the kernel attempts to resolve such deeply nested symlinks, it enters into recursive processing that can lead to significant resource consumption and system instability. This behavior aligns with CWE-674, which describes insufficient recursion protection in software systems. The kernel's path resolution algorithms lack proper depth limits or recursion detection mechanisms, causing the system to spend excessive time and computational cycles traversing these artificial link chains.
The operational impact of this vulnerability extends beyond simple resource exhaustion, as it can effectively render the affected system unusable or significantly degraded. Local users with access to the filesystem can exploit this weakness to create a denial of service condition that affects the entire system. The attack vector is particularly concerning because it requires minimal privileges and can be executed through normal filesystem operations. This vulnerability directly maps to ATT&CK technique T1499.001, which covers network denial of service attacks, though in this case the attack operates at the local kernel level rather than network infrastructure.
Systems affected by this vulnerability demonstrate a predictable failure pattern where the kernel becomes unresponsive during attempts to access deeply nested symbolic links. The resource consumption manifests as high cpu utilization and potential system hangs, making it difficult for legitimate system processes to function properly. The vulnerability affects all Linux systems running the specified kernel versions, regardless of hardware platform or system configuration. Organizations implementing mitigation strategies should consider both immediate patching and implementation of filesystem access controls to limit potential exploitation. The solution requires kernel-level fixes that establish proper recursion limits and depth checking mechanisms for symbolic link resolution, ensuring that the system can gracefully handle even artificially constructed link chains without compromising overall system stability.