CVE-2016-10208 in Linux
Summary
by MITRE
The ext4_fill_super function in fs/ext4/super.c in the Linux kernel through 4.9.8 does not properly validate meta block groups, which allows physically proximate attackers to cause a denial of service (out-of-bounds read and system crash) via a crafted ext4 image.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 11/11/2022
The vulnerability identified as CVE-2016-10208 resides within the ext4 file system implementation of the Linux kernel, specifically in the ext4_fill_super function located in fs/ext4/super.c. This flaw represents a critical security issue that affects Linux kernel versions through 4.9.8, where the kernel fails to adequately validate meta block groups during file system mounting operations. The vulnerability stems from insufficient input validation mechanisms that should have been in place to verify the integrity and proper structure of ext4 file system metadata. Attackers exploiting this weakness can craft malicious ext4 image files that, when mounted, trigger improper memory access patterns leading to system instability.
The technical exploitation of this vulnerability occurs when an attacker creates a specially crafted ext4 file system image with malformed meta block group information. During the file system mounting process, the ext4_fill_super function attempts to parse and validate the superblock and block group descriptors without proper bounds checking. This lack of validation allows the kernel to access memory locations beyond the intended data structures, resulting in out-of-bounds read operations that can crash the system. The vulnerability specifically targets the kernel's memory management subsystem where it processes file system metadata, creating a condition where legitimate file system structures are misinterpreted as valid data, leading to memory corruption. This type of flaw falls under the CWE-129 weakness category, which encompasses improper validation of array indices and buffer overflows in kernel space operations.
The operational impact of CVE-2016-10208 extends beyond simple denial of service scenarios, as it can result in complete system crashes and potential data loss. Attackers with physical access to systems or those capable of delivering malicious file system images through other attack vectors can leverage this vulnerability to disrupt services and potentially gain unauthorized system access. The vulnerability is particularly concerning because it operates at the kernel level, making it difficult to detect and mitigate through traditional user-space security measures. Systems running affected kernel versions are susceptible to exploitation by attackers who can mount crafted ext4 images, potentially leading to persistent system instability. This vulnerability aligns with ATT&CK technique T1068 which involves local privilege escalation through kernel exploits, though the specific vector here targets system availability rather than privilege elevation.
Mitigation strategies for CVE-2016-10208 primarily involve upgrading to patched kernel versions where the validation logic has been enhanced to properly verify meta block group structures during ext4 file system mounting. System administrators should prioritize kernel updates as the most effective remediation approach, particularly for systems handling untrusted file system images. Additional protective measures include implementing strict file system validation policies for external storage devices, monitoring for unusual file system mounting activities, and ensuring that only trusted users can mount file systems with elevated privileges. The vulnerability demonstrates the importance of robust input validation in kernel space operations and highlights the need for comprehensive testing of file system parsers against malformed data inputs. Organizations should also consider implementing network segmentation and access controls to limit exposure to potential attackers who might attempt to deliver malicious file system images through various attack vectors.