CVE-2006-4342 in Red Hat
Summary
by MITRE
The kernel in Red Hat Enterprise Linux 3, when running on SMP systems, allows local users to cause a denial of service (deadlock) by running the shmat function on an shm at the same time that shmctl is removing that shm (IPC_RMID), which prevents a spinlock from being unlocked.
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Analysis
by VulDB Data Team • 04/24/2026
The vulnerability described in CVE-2006-4342 represents a critical race condition within the Linux kernel's shared memory management subsystem on symmetric multiprocessing systems. This flaw specifically affects Red Hat Enterprise Linux 3 deployments where multiple processors execute concurrently, creating an environment susceptible to timing-dependent failures that can lead to system-wide operational disruption.
The technical implementation of this vulnerability stems from improper synchronization mechanisms within the kernel's inter-process communication subsystem. When a local user executes the shmat system call to attach to a shared memory segment while simultaneously another process invokes shmctl with the IPC_RMID flag to remove that same segment, the kernel's internal spinlock mechanism becomes corrupted. The spinlock, which should normally be acquired and released in a predictable sequence, fails to unlock properly due to the concurrent execution paths, resulting in a deadlock state that prevents further system operations.
This vulnerability operates under the context of privilege escalation and system stability concerns, as it can be exploited by any local user with access to the system, making it particularly dangerous in multi-user environments. The denial of service condition manifests as a complete system lockup where the affected processor cores become unresponsive to further system calls, effectively rendering the entire system unavailable for legitimate operations. The issue is classified as a race condition under CWE-362, which specifically addresses concurrent execution issues that can lead to security vulnerabilities.
The operational impact of this vulnerability extends beyond simple service disruption, as it can compromise the availability of critical system services and applications that depend on shared memory communication. In enterprise environments running Red Hat Enterprise Linux 3, this flaw could potentially be exploited to cause significant downtime, affecting business operations and potentially leading to financial losses. The vulnerability's exploitation requires minimal privileges and can be executed without requiring elevated access rights, making it particularly concerning for system administrators.
Mitigation strategies for this vulnerability include applying the appropriate kernel patches provided by Red Hat, which address the synchronization issues in the shared memory management code. System administrators should also consider implementing monitoring solutions to detect anomalous shared memory usage patterns that might indicate exploitation attempts. The fix typically involves modifying the kernel's spinlock acquisition and release mechanisms to ensure proper handling of concurrent shmat and shmctl operations, preventing the deadlock condition from occurring. Additionally, organizations should consider upgrading to newer versions of Red Hat Enterprise Linux that contain these fixes and have improved concurrency handling mechanisms. This vulnerability demonstrates the importance of proper synchronization in kernel-level code and aligns with ATT&CK technique T1499.004 for denial of service attacks targeting system resources.