CVE-2006-5754 in Linux
Summary
by MITRE
The aio_setup_ring function in Linux kernel does not properly initialize a variable, which allows local users to cause a denial of service (crash) via an unspecified error path that causes an incorrect free operation.
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Analysis
by VulDB Data Team • 07/14/2019
The vulnerability identified as CVE-2006-5754 resides within the Linux kernel's asynchronous input/output subsystem, specifically in the aio_setup_ring function that manages the setup of asynchronous I/O rings for kernel-level operations. This flaw represents a classic case of improper variable initialization that manifests through an incorrect memory management operation during kernel execution. The vulnerability affects systems running Linux kernel versions prior to the patch release that addressed this issue, creating a persistent risk for local attackers who can exploit the uninitialized variable to trigger system instability. The flaw operates at the kernel level where memory management operations are critical and any deviation from expected behavior can result in catastrophic system failure.
The technical root cause of this vulnerability stems from the aio_setup_ring function failing to properly initialize a variable before its use in memory allocation and deallocation operations. When the function processes asynchronous I/O ring setup requests, it encounters an error path where an uninitialized variable is used to determine memory management operations. This uninitialized state leads to unpredictable behavior during the subsequent free operation, where the kernel attempts to free memory using incorrect parameters. The vulnerability falls under CWE-457, which specifically addresses the use of uninitialized variables in software development, and demonstrates how such issues can be leveraged for denial of service attacks at the kernel level. The improper initialization creates a condition where the kernel's memory management subsystem receives malformed parameters, causing the system to crash when attempting to free the incorrectly calculated memory addresses.
The operational impact of this vulnerability extends beyond simple system instability, as it provides local attackers with a reliable method for causing system-wide denial of service conditions. The attack vector requires local access to the system, making it particularly concerning for environments where privilege separation is not properly enforced. When exploited, the vulnerability can cause the kernel to crash and potentially trigger a system reboot, resulting in service disruption and potential data loss. The attack is particularly effective because it targets fundamental kernel operations that are frequently accessed during normal system operation, making it difficult to prevent through simple access controls. This vulnerability also aligns with ATT&CK technique T1499.004, which describes the use of system resource exhaustion and kernel-level attacks to cause denial of service conditions in operating systems.
Mitigation strategies for CVE-2006-5754 focus primarily on applying the appropriate kernel security patches released by the Linux kernel development team. System administrators should prioritize updating their kernel versions to include the fix that properly initializes the variable in the aio_setup_ring function, ensuring that all memory management operations occur with valid parameters. Additionally, implementing proper privilege separation and limiting local user access to systems can reduce the attack surface for exploitation. Monitoring systems should be configured to detect unusual kernel crash patterns or memory management errors that might indicate exploitation attempts. Organizations should also consider implementing kernel hardening techniques such as stack canaries and address space layout randomization to make exploitation more difficult. The vulnerability serves as a reminder of the critical importance of proper variable initialization in kernel code and the necessity of thorough code reviews and testing procedures for low-level system components.