CVE-2014-0203 in Linux
Summary
by MITRE
The __do_follow_link function in fs/namei.c in the Linux kernel before 2.6.33 does not properly handle the last pathname component during use of certain filesystems, which allows local users to cause a denial of service (incorrect free operations and system crash) via an open system call.
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Analysis
by VulDB Data Team • 08/01/2021
The vulnerability described in CVE-2014-0203 represents a critical flaw in the Linux kernel's pathname resolution mechanism that affects systems running kernel versions prior to 2.6.33. This issue resides within the __do_follow_link function located in the fs/namei.c file, which is responsible for handling symbolic link resolution and pathname traversal operations. The flaw manifests when the kernel processes certain filesystem operations that involve the final component of a pathname, creating a condition where incorrect memory management occurs during the open system call execution. This vulnerability falls under the category of improper handling of pathname components and memory allocation errors, which are commonly classified as CWE-457 and CWE-787 respectively.
The technical exploitation of this vulnerability occurs when a local attacker crafts specific filesystem operations that trigger the problematic code path in the kernel's name resolution subsystem. During the execution of the open system call, the kernel's __do_follow_link function fails to properly manage the memory associated with the final pathname component, leading to incorrect free operations that can result in memory corruption. This memory corruption manifests as system crashes or denial of service conditions, effectively allowing attackers to disrupt system operations without requiring elevated privileges. The vulnerability is particularly dangerous because it operates at the kernel level and can be triggered through legitimate system calls, making detection and prevention challenging. According to ATT&CK framework, this vulnerability maps to T1068 (Local Privilege Escalation) and T1499.004 (Endpoint Denial of Service) tactics, as it enables local users to cause system instability.
The operational impact of CVE-2014-0203 extends beyond simple denial of service, as it can potentially lead to complete system crashes and require manual intervention for recovery. Systems running affected kernel versions are particularly vulnerable when handling complex filesystem operations involving symbolic links and nested directory structures. The vulnerability affects various filesystem types that rely on the name resolution code path, making it widespread across different system configurations. Organizations with multiple systems running older kernel versions face significant risk, as the vulnerability can be exploited through normal user activities without requiring special privileges or network access. The exploitability is high for local users who can manipulate filesystem operations to trigger the memory corruption, and the impact is severe as it can render systems unusable until reboot or manual intervention. This vulnerability underscores the critical importance of kernel security updates and proper system maintenance practices to prevent exploitation of such fundamental memory management flaws.