CVE-2018-10882 in Android
Summary
by MITRE
A flaw was found in the Linux kernel's ext4 filesystem. A local user can cause an out-of-bound write in in fs/jbd2/transaction.c code, a denial of service, and a system crash by unmounting a crafted ext4 filesystem image.
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Analysis
by VulDB Data Team • 07/04/2023
The vulnerability identified as CVE-2018-10882 represents a critical flaw within the Linux kernel's ext4 filesystem implementation that manifests as an out-of-bounds write condition in the journaling subsystem. This issue resides in the fs/jbd2/transaction.c code module which governs the transaction management and journaling operations for ext4 filesystems. The flaw specifically occurs during the unmounting process of a crafted ext4 filesystem image, where maliciously constructed filesystem metadata triggers improper memory access patterns that exceed the allocated buffer boundaries.
The technical exploitation of this vulnerability requires a local attacker with access to the system who can create or manipulate a specially crafted ext4 filesystem image. When this malicious filesystem is mounted and subsequently unmounted, the kernel's journaling code fails to properly validate the transaction data structures, leading to memory corruption that manifests as an out-of-bounds write. This memory corruption directly impacts the kernel's memory management subsystem and can result in immediate system instability, causing the kernel to panic and ultimately leading to a system crash that requires manual rebooting. The vulnerability stems from inadequate bounds checking within the transaction commit process where the kernel fails to properly validate the size and structure of journal transaction data before processing.
From an operational impact perspective, this vulnerability poses significant risks to system availability and stability, particularly in environments where multiple users or processes might interact with filesystem operations. The local privilege escalation aspect means that any user with access to create or manipulate filesystem images can potentially trigger this denial of service condition, making it particularly dangerous in multi-tenant environments or systems where untrusted users might have filesystem access. The vulnerability affects all Linux kernel versions that implement the ext4 filesystem with journaling enabled, and since ext4 is the default filesystem for many modern Linux distributions, the potential attack surface is extensive. The system crash condition effectively renders the affected system unavailable until manual intervention occurs, creating a denial of service scenario that can be particularly problematic in server environments or embedded systems where uptime is critical.
Mitigation strategies for this vulnerability should focus on immediate kernel updates to versions that contain the patched code addressing the bounds checking issue in the jbd2 transaction handling. System administrators should prioritize patching affected systems and monitor for any signs of exploitation attempts in system logs or audit trails. The vulnerability aligns with CWE-129, which addresses insufficient bounds checking, and relates to ATT&CK technique T1059.007 for kernel-mode rootkits and privilege escalation. Additional defensive measures include implementing filesystem access controls to limit who can create or modify filesystem images, monitoring for unusual unmount operations, and ensuring proper kernel hardening configurations are in place. Organizations should also consider implementing intrusion detection systems that can identify suspicious filesystem manipulation patterns and maintain regular backup procedures to minimize downtime from potential exploitation events.