CVE-2014-9729 in Linux
Summary
by MITRE
The udf_read_inode function in fs/udf/inode.c in the Linux kernel before 3.18.2 does not ensure a certain data-structure size consistency, which allows local users to cause a denial of service (system crash) via a crafted UDF filesystem image.
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Analysis
by VulDB Data Team • 05/20/2022
The vulnerability identified as CVE-2014-9729 resides within the Linux kernel's Universal Disk Format UDF filesystem implementation, specifically in the udf_read_inode function located in fs/udf/inode.c. This flaw represents a classic case of insufficient input validation and data structure consistency checking that can be exploited by local attackers to trigger system instability. The vulnerability affects Linux kernel versions prior to 3.18.2, making it a significant concern for systems running older kernel versions that have not been properly updated.
The technical root cause of this vulnerability stems from the udf_read_inode function's failure to validate the consistency of data structure sizes when processing UDF filesystem images. When a maliciously crafted UDF filesystem image is mounted, the function does not properly verify that the expected data structures conform to their defined size requirements. This oversight creates a condition where the kernel's UDF filesystem driver can encounter malformed data structures that cause memory access violations or other internal inconsistencies during inode processing. The vulnerability manifests as a system crash or kernel panic when the kernel attempts to read and process these malformed inode structures, effectively resulting in a denial of service condition that can bring the entire system to a halt.
From an operational perspective, this vulnerability presents a significant risk to local attackers who can leverage it to perform denial of service attacks against Linux systems running vulnerable kernel versions. The attack requires local access to the system since the vulnerability is triggered during filesystem mounting operations, making it a local privilege escalation vector that can be exploited by users with minimal system access. The impact extends beyond simple service disruption as system crashes can result in data loss, corruption of running processes, and potential compromise of system availability for legitimate users. The vulnerability is particularly concerning in multi-user environments or systems where untrusted users have access to filesystem mounting capabilities, as it can be used to disrupt system operations without requiring elevated privileges.
The vulnerability aligns with CWE-129, which addresses insufficient input validation, and can be mapped to ATT&CK technique T1499.004 for denial of service attacks. This mapping reflects how the vulnerability enables attackers to disrupt system services through kernel-level memory corruption. The flaw demonstrates the critical importance of robust input validation in kernel space code, where malformed inputs can lead to system crashes rather than simple application failures. The attack surface is limited to systems that mount UDF filesystems, which includes optical media, digital video discs, and other storage formats that utilize the UDF filesystem. Organizations should prioritize kernel updates to address this vulnerability, as the fix implemented in kernel version 3.18.2 ensures proper size validation of UDF data structures before processing them. Additionally, system administrators should consider implementing filesystem access controls and monitoring for suspicious UDF image mounting attempts to detect potential exploitation attempts.
The remediation approach for CVE-2014-9729 involves upgrading to Linux kernel version 3.18.2 or later, which contains the necessary patches to validate UDF data structure sizes properly. System administrators should also implement comprehensive patch management procedures to ensure all vulnerable systems receive timely updates. The vulnerability highlights the importance of maintaining current kernel versions and implementing automated patching strategies to protect against known vulnerabilities. Organizations should conduct regular vulnerability assessments to identify systems running outdated kernel versions and prioritize their remediation to prevent exploitation of similar kernel-level vulnerabilities. The fix demonstrates the effectiveness of proper input validation and data structure consistency checking in preventing kernel-level denial of service conditions that can compromise system stability and availability.