CVE-2012-6548 in Linux
Summary
by MITRE
The udf_encode_fh function in fs/udf/namei.c in the Linux kernel before 3.6 does not initialize a certain structure member, which allows local users to obtain sensitive information from kernel heap memory via a crafted application.
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Analysis
by VulDB Data Team • 01/01/2022
The vulnerability identified as CVE-2012-6548 represents a classic information disclosure flaw within the Linux kernel's Unified Data Format UDF (Universal Disk Format) implementation. This issue resides in the udf_encode_fh function located in fs/udf/namei.c, a critical component responsible for handling file handle encoding operations within the UDF filesystem driver. The vulnerability manifests when the function fails to properly initialize a specific structure member during its execution, creating a potential pathway for unauthorized data exposure.
The technical root cause of this vulnerability stems from inadequate memory initialization practices within the kernel's filesystem handling code. When the udf_encode_fh function processes file handle encoding requests, it neglects to initialize certain structure members before returning data to user-space applications. This initialization oversight results in the unintentional exposure of uninitialized memory contents that may contain sensitive data remnants from previous kernel operations, including potentially confidential information from other processes or kernel structures. The flaw operates at the kernel level and specifically affects systems running Linux kernel versions prior to 3.6, making it a significant concern for organizations maintaining older kernel versions.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates opportunities for local attackers to potentially gather sensitive kernel memory contents that could reveal system internals, process information, or other confidential data. Attackers could exploit this weakness by crafting specific applications that invoke the udf_encode_fh function repeatedly, gradually collecting memory fragments that might contain useful information for further exploitation attempts. This type of information leakage could potentially aid in bypassing security mechanisms or understanding system behavior, particularly in environments where multiple processes interact with UDF filesystems.
This vulnerability aligns with CWE-119, which addresses improper access to memory buffers, and represents a specific instance of information exposure through uninitialized memory. The flaw demonstrates characteristics consistent with ATT&CK technique T1005, which involves data from local system storage, as it enables unauthorized access to kernel memory contents that would normally remain protected. From a security perspective, this issue exemplifies the importance of proper memory initialization practices in kernel code, as even seemingly minor oversights can create significant security implications. The vulnerability also reflects the broader category of kernel memory corruption issues that can lead to privilege escalation or information disclosure attacks, making it a critical concern for system administrators managing Linux environments.
The recommended mitigation strategy involves upgrading to Linux kernel version 3.6 or later, where the memory initialization issue has been resolved through proper code modifications. System administrators should prioritize this update across all affected systems, particularly those handling UDF filesystems or operating in security-sensitive environments. Additionally, organizations should implement comprehensive patch management processes to ensure timely deployment of kernel security updates. Monitoring for unusual file handle operations or memory access patterns could provide early detection of potential exploitation attempts, while maintaining current kernel versions serves as the primary defense against this specific vulnerability and similar memory-related issues.