CVE-2005-4811 in Linux
Summary
by MITRE
The hugepage code (hugetlb.c) in Linux kernel 2.6, possibly 2.6.12 and 2.6.13, in certain configurations, allows local users to cause a denial of service (crash) by triggering an mmap error before a prefault, which causes an error in the unmap_hugepage_area function.
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Analysis
by VulDB Data Team • 07/09/2019
The vulnerability described in CVE-2005-4811 resides within the huge page implementation of the Linux kernel version 2.6, specifically affecting kernel versions including 2.6.12 and 2.6.13. This issue manifests in the hugetlb.c file which handles huge page memory management, a critical component for systems requiring high-performance memory operations. The vulnerability represents a local privilege escalation risk that can result in system instability and denial of service conditions, making it particularly concerning for production environments where system reliability is paramount.
The technical flaw occurs when specific memory mapping configurations trigger an mmap error prior to the prefault phase in the huge page allocation process. This sequence creates a condition where the unmap_hugepage_area function encounters an error state that leads to a kernel crash. The vulnerability exploits the interaction between memory management subsystems and the huge page handling code, specifically when the kernel attempts to clean up memory mappings during error conditions. This represents a classic buffer overflow or memory corruption scenario where improper error handling leads to system instability.
The operational impact of this vulnerability extends beyond simple denial of service as it can cause complete system crashes, potentially leading to data loss and service interruptions. Local attackers who have access to the system can exploit this weakness to disrupt normal operations, making it particularly dangerous in multi-user environments or systems where unprivileged users have access to memory allocation mechanisms. The vulnerability affects systems that utilize huge page memory management, which are commonly found in high-performance computing environments, database servers, and applications requiring large memory allocations.
Mitigation strategies for this vulnerability include applying the appropriate kernel security patches released by the Linux kernel development team, which address the improper error handling in the huge page management code. System administrators should also implement monitoring solutions to detect unusual memory allocation patterns that might indicate exploitation attempts. Additionally, organizations should consider disabling huge page support if it is not essential for their workloads, though this approach may impact performance for applications that specifically benefit from huge page usage. This vulnerability aligns with CWE-248, which covers "Uncaught Exception" in software systems, and represents a failure in proper error state management within kernel space operations.
The attack surface for this vulnerability is limited to local users with access to the system, but the potential impact is significant as it can cause complete system crashes. Security teams should prioritize patching this vulnerability, especially in environments where the kernel is running with huge page support enabled. Organizations should also conduct regular security assessments of their kernel configurations to ensure that unnecessary memory management features are disabled. The vulnerability demonstrates the critical importance of proper error handling in kernel space code and the potential for seemingly minor implementation flaws to cause catastrophic system failures.
This particular vulnerability underscores the complexity of memory management in operating systems and the critical nature of kernel code validation. The interaction between different memory subsystems in the Linux kernel creates potential points of failure that can be exploited through careful manipulation of system calls and memory allocation patterns. The patch for this vulnerability addresses the specific error handling path in the hugetlb.c file, ensuring that error conditions are properly managed during huge page operations. System administrators should also consider implementing additional security controls such as kernel hardening measures and memory protection mechanisms to reduce the overall attack surface.
The broader implications of this vulnerability extend to the security practices of kernel development, emphasizing the need for comprehensive testing of error handling paths in critical system components. This vulnerability demonstrates how memory management subsystems can introduce instability when not properly validated under all operational conditions. Organizations should maintain up-to-date security practices and regularly review their kernel configurations to ensure that all known vulnerabilities are addressed. The vulnerability also highlights the importance of proper code review processes in kernel development, where edge cases and error conditions should be thoroughly tested to prevent similar issues from occurring in production environments.
The remediation approach for CVE-2005-4811 requires immediate kernel updates from the vendor, as the vulnerability exists within core kernel memory management functionality. Security teams should also implement monitoring to detect unusual memory allocation patterns that might indicate exploitation attempts, though the local nature of the attack limits the scope of external detection. The vulnerability represents a failure in the ATT&CK framework's privilege escalation techniques, specifically targeting kernel-level memory management operations. Organizations should ensure that their patch management processes include verification of kernel security updates, particularly for critical memory management components that can lead to system instability and denial of service conditions.