CVE-2005-3784 in Linux
Summary
by MITRE
The auto-reap of child processes in Linux kernel 2.6 before 2.6.15 includes processes with ptrace attached, which leads to a dangling ptrace reference and allows local users to cause a denial of service (crash) and gain root privileges.
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Analysis
by VulDB Data Team • 06/12/2019
The vulnerability described in CVE-2005-3784 represents a critical race condition in the Linux kernel's process management subsystem that affects versions prior to 2.6.15. This flaw specifically targets the auto-reap mechanism responsible for cleaning up terminated child processes, creating a scenario where processes with ptrace attachments are incorrectly included in the reaping process. The vulnerability operates at the kernel level and demonstrates a fundamental flaw in process lifecycle management that has far-reaching implications for system security and stability.
The technical implementation of this vulnerability stems from the kernel's improper handling of ptrace references during process termination. When a parent process creates a child process that is subsequently attached to using ptrace for debugging or monitoring purposes, the kernel must maintain a reference to this relationship until both processes are properly terminated. However, in affected kernel versions, the auto-reap mechanism fails to distinguish between regular child processes and those with active ptrace attachments. This oversight results in the kernel attempting to reap a process that still maintains a valid ptrace reference, creating a dangling reference that can cause memory corruption and system instability.
The operational impact of this vulnerability is severe and multifaceted, providing attackers with both denial of service capabilities and privilege escalation opportunities. Local users can exploit this flaw to crash the system through carefully crafted process termination sequences that trigger the dangling ptrace reference condition. More critically, the vulnerability allows attackers to gain root privileges by leveraging the improper reference handling to manipulate kernel memory structures and escalate their privileges. This dual nature makes the vulnerability particularly dangerous as it can be exploited by any local user with basic system access, potentially leading to complete system compromise.
The vulnerability aligns with CWE-367, which addresses Time-of-Check to Time-of-Use (TOCTOU) flaws in process management, and demonstrates characteristics consistent with ATT&CK technique T1068, which involves the exploitation of privilege escalation vulnerabilities in operating systems. The flaw represents a classic example of improper resource management where the kernel fails to properly synchronize process termination with ptrace reference management, creating a window where inconsistent state can be exploited. This vulnerability specifically affects the kernel's process management subsystem and requires immediate patching to prevent exploitation, as it fundamentally undermines the security model of the Linux operating system by allowing local users to bypass privilege boundaries and cause system crashes.
Mitigation strategies for this vulnerability focus primarily on kernel version updates to 2.6.15 or later, which contain the necessary patches to properly handle ptrace references during process termination. System administrators should also implement process monitoring to detect unusual ptrace activity and consider restricting ptrace capabilities in production environments where possible. The vulnerability serves as a reminder of the critical importance of proper kernel resource management and the potential for seemingly minor flaws in system-level code to create significant security risks that can be exploited for both denial of service and privilege escalation attacks.