CVE-2003-0127 in Linux
Summary
by MITRE
The kernel module loader in Linux kernel 2.2.x before 2.2.25, and 2.4.x before 2.4.21, allows local users to gain root privileges by using ptrace to attach to a child process that is spawned by the kernel.
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Analysis
by VulDB Data Team • 08/24/2025
The vulnerability described in CVE-2003-0127 represents a critical privilege escalation flaw within the Linux kernel's module loading mechanism. This vulnerability affects kernel versions 2.2.x prior to 2.2.25 and 2.4.x prior to 2.4.21, creating a significant security gap that local attackers can exploit to elevate their privileges from standard user level to root access. The flaw specifically targets the interaction between the ptrace system call and kernel module loading processes, demonstrating how improper privilege handling in kernel space can lead to system compromise.
The technical implementation of this vulnerability exploits the timing and privilege relationship between parent and child processes during kernel module loading operations. When a kernel module loader spawns a child process to perform specific tasks, a local user with ptrace capabilities can attach to this child process and manipulate its execution flow. This manipulation allows the attacker to inject malicious code or modify the module loading process itself, ultimately gaining root privileges through the elevated permissions required for kernel module operations. The vulnerability stems from insufficient privilege checks during the module loading sequence, where the system fails to properly validate the security context of processes involved in kernel module operations.
From an operational perspective, this vulnerability presents a severe threat to system integrity as it requires minimal privileges for exploitation and provides maximum impact. An attacker need only have local access to a system running vulnerable kernel versions to potentially gain complete control. The attack vector leverages the ptrace system call, which is commonly available to regular users for debugging purposes, making this vulnerability particularly dangerous in multi-user environments. The vulnerability's exploitation process involves carefully timed attachment to kernel processes, followed by privilege elevation through module loading mechanisms, representing a sophisticated attack pattern that aligns with techniques described in the ATT&CK framework under privilege escalation tactics.
The root cause of this vulnerability can be categorized under CWE-276, which addresses improper privilege management in operating systems. The flaw demonstrates inadequate access control mechanisms during kernel module operations, where the system fails to properly enforce privilege boundaries between user-space processes and kernel-space operations. This weakness creates a direct pathway for local privilege escalation, as the ptrace attachment allows manipulation of kernel processes that should normally be protected from user interference. The vulnerability also reflects broader issues in kernel security design where process management and privilege separation are not properly enforced during critical system operations.
Mitigation strategies for CVE-2003-0127 focus primarily on kernel version updates and system hardening measures. Organizations should immediately upgrade to kernel versions 2.2.25 or later for 2.2.x series and 2.4.21 or later for 2.4.x series to address the vulnerability. System administrators should also implement proper access controls to limit ptrace usage and monitor for unauthorized ptrace operations. Additionally, the principle of least privilege should be enforced by restricting user access to debugging capabilities and implementing kernel lockdown mechanisms. The vulnerability serves as a reminder of the critical importance of proper privilege management in kernel space operations and demonstrates how seemingly benign system calls can be exploited for privilege escalation attacks.