CVE-2009-4306 in Linux
Summary
by MITRE
Unspecified vulnerability in the EXT4_IOC_MOVE_EXT (aka move extents) ioctl implementation in the ext4 filesystem in the Linux kernel 2.6.32-git6 and earlier allows local users to cause a denial of service (filesystem corruption) via unknown vectors, a different vulnerability than CVE-2009-4131.
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Analysis
by VulDB Data Team • 08/28/2021
The vulnerability described in CVE-2009-4306 represents a critical flaw in the Linux kernel's ext4 filesystem implementation that affects versions 2.6.32-git6 and earlier. This issue resides within the EXT4_IOC_MOVE_EXT ioctl operation which is designed to move data extents from one location to another within the same filesystem. The unspecified nature of the vulnerability vectors makes this particularly dangerous as it could potentially be exploited through multiple attack paths. The flaw enables local users to trigger filesystem corruption rather than simply causing a denial of service, which represents a more severe impact than typical denial of service conditions. This vulnerability is distinct from CVE-2009-4131, indicating that it operates through different mechanisms within the filesystem layer. The vulnerability affects the core filesystem operations that manage how data is organized and stored on disk, making it a fundamental security concern for any system relying on ext4 filesystems.
The technical implementation of this vulnerability stems from improper validation and handling of parameters within the ext4 filesystem's move extents ioctl handler. When a local user executes the EXT4_IOC_MOVE_EXT operation, the kernel's filesystem layer fails to properly validate input parameters or maintain proper data structures during the move operation. This lack of proper bounds checking and state management can lead to memory corruption or data structure inconsistencies that ultimately result in filesystem corruption. The vulnerability likely involves buffer overflows, integer overflows, or improper pointer management within the kernel's filesystem code that handles extent movement operations. According to CWE classification, this vulnerability would likely fall under CWE-121, heap-based buffer overflow, or CWE-122, stack-based buffer overflow, depending on the specific implementation flaw. The attack vector requires local access to the system since the vulnerability is in a kernel-level filesystem operation that typically requires elevated privileges or at least local user access.
The operational impact of CVE-2009-4306 extends beyond simple denial of service to include potential data loss and filesystem instability that could compromise entire system operations. When filesystem corruption occurs, it can render files inaccessible, cause data to become fragmented, or even result in complete filesystem unmounting. This vulnerability poses significant risk to servers and workstations that rely on ext4 filesystems, as local attackers could systematically corrupt filesystem data to cause service disruption. The impact is particularly severe in environments where data integrity is critical, such as database servers, file servers, or systems handling sensitive information. The vulnerability's potential for causing permanent data loss means that even successful exploitation may require extensive recovery procedures including filesystem checks, data restoration from backups, and system reinstallation. Organizations running affected kernel versions face the risk of operational downtime, data recovery costs, and potential compliance violations if data integrity is compromised.
Mitigation strategies for CVE-2009-4306 should focus on immediate kernel updates to versions that have patched the vulnerability, as this represents the most effective defense against exploitation. System administrators should prioritize updating to kernel versions 2.6.33 or later where the vulnerability has been addressed through proper input validation and state management within the ext4 filesystem code. Additionally, implementing access controls to limit local user privileges can reduce the attack surface, though this does not prevent exploitation by users with sufficient privileges. Monitoring for unusual filesystem behavior or corruption patterns can help detect exploitation attempts, and regular filesystem checks using tools like e2fsck can identify corruption before it becomes critical. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving privilege escalation and denial of service, but the filesystem corruption aspect introduces additional persistence and data integrity compromise capabilities. Organizations should also consider implementing automated patch management systems to ensure rapid deployment of security updates across all affected systems, particularly given that this vulnerability affects widely deployed kernel versions from 2009. The remediation process should include comprehensive testing of filesystem operations after patching to ensure that no residual issues remain and that the filesystem functionality operates correctly.