CVE-2014-9730 in Linux
Summary
by MITRE
The udf_pc_to_char function in fs/udf/symlink.c in the Linux kernel before 3.18.2 relies on component lengths that are unused, 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-2014-9730 represents a critical flaw in the Linux kernel's Universal Disk Format implementation that affects systems running kernel versions prior to 3.18.2. This issue resides within the udf_pc_to_char function located in the fs/udf/symlink.c file, where the kernel fails to properly validate component lengths during UDF filesystem processing. The flaw specifically manifests when the kernel encounters crafted UDF filesystem images that contain malformed component length values, creating a scenario where unused but referenced data structures can trigger unexpected behavior. The vulnerability operates at the filesystem level and demonstrates how improper input validation can lead to system instability, making it particularly dangerous for systems that handle untrusted filesystem images.
The technical exploitation of this vulnerability occurs through a classic buffer overread or memory access violation pattern that falls under CWE-129, which addresses improper validation of array indices. When the udf_pc_to_char function processes a UDF filesystem image with maliciously constructed component length values, it attempts to access memory locations that were never properly initialized or validated. This leads to a kernel panic or system crash, effectively creating a denial of service condition that can be triggered by any local user with access to create or mount a crafted UDF filesystem image. The vulnerability is particularly insidious because it does not require elevated privileges for exploitation, as local users can craft the malicious filesystem image and mount it to trigger the kernel crash.
From an operational impact perspective, this vulnerability creates significant security implications for Linux systems that may encounter untrusted UDF filesystems, which commonly occur in environments where removable media, optical discs, or network storage systems are used. The denial of service nature means that systems could become unavailable to legitimate users, potentially disrupting critical services or causing cascading failures in larger networked environments. The ATT&CK framework categorizes this vulnerability under T1499.004, which covers "Network Denial of Service" and T1068, "Exploitation for Privilege Escalation," though the latter is less applicable due to the local nature of the exploit. Organizations using Linux systems in enterprise environments, cloud infrastructures, or any setting where untrusted storage media might be mounted face substantial risk from this vulnerability.
The mitigation strategy for CVE-2014-9730 primarily involves upgrading to Linux kernel version 3.18.2 or later, where the vulnerability has been patched through proper validation of component lengths within the udf_pc_to_char function. Additionally, system administrators should implement strict filesystem mounting policies that prevent automatic mounting of untrusted UDF images, particularly when these images originate from removable media or network shares. The patch addresses the root cause by ensuring that component length values are properly validated before being used in memory access operations, thereby preventing the kernel from attempting to access invalid memory locations. Organizations should also consider implementing monitoring solutions that can detect unusual filesystem mounting activities or kernel panic events that might indicate exploitation attempts. Regular kernel updates and security audits remain crucial for maintaining system integrity, especially in environments where legacy systems might be running vulnerable kernel versions.