CVE-2018-10881 in Linux
Summary
by MITRE
A flaw was found in the Linux kernel's ext4 filesystem. A local user can cause an out-of-bound access in ext4_get_group_info function, a denial of service, and a system crash by mounting and operating on a crafted ext4 filesystem image.
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Analysis
by VulDB Data Team • 04/27/2023
The vulnerability identified as CVE-2018-10881 represents a critical out-of-bounds memory access flaw within the Linux kernel's ext4 filesystem implementation. This issue manifests specifically within the ext4_get_group_info function, which handles group descriptor management for ext4 filesystems. The flaw occurs when a local user mounts and operates on a specially crafted ext4 filesystem image, triggering unauthorized memory access patterns that can lead to system instability. The vulnerability exploits the kernel's handling of filesystem group information structures, where insufficient bounds checking allows memory operations to exceed allocated buffer boundaries. This type of flaw falls under the CWE-129 vulnerability category, which encompasses issues related to insufficient bounds checking in array access operations.
The operational impact of this vulnerability extends beyond simple denial of service to potentially causing complete system crashes and destabilization of the kernel's memory management subsystem. When the malicious filesystem is mounted and accessed, the ext4_get_group_info function processes group descriptor information without proper validation of the input parameters, leading to memory corruption that can result in kernel panics or system lockups. The local privilege requirement means that an attacker with access to the system must create and mount the malicious filesystem to exploit this vulnerability, making it less likely to be exploited remotely but still posing significant risks in multi-user environments where local access is possible. The vulnerability demonstrates characteristics consistent with ATT&CK technique T1068, which involves local privilege escalation through kernel exploits, though in this case the immediate impact is denial of service rather than privilege escalation.
The technical exploitation requires careful construction of an ext4 filesystem image that contains malformed group descriptor information, specifically designed to trigger the out-of-bounds access during normal filesystem operations. This attack vector represents a classic kernel memory corruption vulnerability that can be leveraged to disrupt system availability and potentially serve as a stepping stone for more sophisticated attacks. The flaw affects all Linux kernel versions that implement the ext4 filesystem with the vulnerable group information handling code, making it widespread across numerous distributions and system configurations. System administrators should prioritize applying kernel updates that include patches addressing this specific memory access violation in the ext4 filesystem driver. The vulnerability also highlights the importance of filesystem image validation and the need for robust input sanitization in kernel-level code handling filesystem metadata. Organizations should implement monitoring for unusual filesystem access patterns and ensure regular kernel patching to mitigate the risk of exploitation. The security implications extend to any system that relies on ext4 filesystems for data storage, including servers, desktops, and embedded systems where local access might be compromised.