CVE-2018-10883 in Linux
Summary
by MITRE
A flaw was found in the Linux kernel's ext4 filesystem. A local user can cause an out-of-bounds write in jbd2_journal_dirty_metadata(), 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-2018-10883 represents a critical flaw in the Linux kernel's ext4 filesystem implementation that manifests through the jbd2_journal_dirty_metadata() function. This issue affects the journaling component of ext4 filesystems, specifically within the kernel's journaling block device subsystem. The vulnerability arises from improper bounds checking during metadata operations, creating a scenario where maliciously crafted filesystem images can trigger memory corruption. The flaw exists at the intersection of filesystem management and kernel memory handling, making it particularly dangerous as it can be exploited through local user access to filesystem images.
The technical implementation of this vulnerability stems from inadequate input validation within the journaling subsystem when processing metadata updates. When a crafted ext4 filesystem image is mounted, the jbd2_journal_dirty_metadata() function fails to properly verify array bounds during metadata write operations, leading to out-of-bounds memory writes. This memory corruption occurs in kernel space, bypassing typical user-space protections and security mechanisms. The vulnerability is classified under CWE-129 as an insufficient bounds checking issue, specifically manifesting as an out-of-bounds write condition that can be exploited through crafted input data. The attack vector requires local access to mount and interact with the malicious filesystem image, but the impact extends to system stability and availability.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attacks. System crashes and kernel oops messages occur when the out-of-bounds write corrupts critical kernel memory structures, leading to immediate system instability. The vulnerability affects all Linux kernel versions that include the affected ext4 filesystem implementation, creating widespread exposure across various distributions and deployment scenarios. This flaw can be particularly problematic in environments where users have the ability to mount filesystem images, such as in virtualized environments, containerized deployments, or systems handling untrusted storage media. The vulnerability's classification under the ATT&CK technique T1068 (Local Privilege Escalation) indicates potential for escalation beyond initial denial of service conditions, though the primary impact remains system instability and crash conditions.
Mitigation strategies for CVE-2018-10883 focus primarily on kernel updates and filesystem validation practices. System administrators should immediately apply the relevant kernel security patches that address the bounds checking issues in jbd2_journal_dirty_metadata() function. The vulnerability can also be mitigated through filesystem validation and image scanning processes that prevent mounting of untrusted ext4 images. Additionally, implementing proper access controls and limiting local user privileges can reduce the attack surface, as exploitation requires local access to mount and operate on the crafted filesystem. Organizations should also consider deploying kernel security modules and monitoring systems that can detect anomalous filesystem behavior patterns. The fix typically involves adding proper bounds checking to the journaling subsystem to prevent the out-of-bounds memory write conditions that lead to system crashes and denial of service scenarios.