CVE-2013-4516 in Linux
Summary
by MITRE
The mp_get_count function in drivers/staging/sb105x/sb_pci_mp.c in the Linux kernel before 3.12 does not initialize a certain data structure, which allows local users to obtain sensitive information from kernel stack memory via a TIOCGICOUNT ioctl call.
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Analysis
by VulDB Data Team • 06/01/2021
The vulnerability identified as CVE-2013-4516 represents a classic information disclosure flaw within the Linux kernel's serial communication driver subsystem. This issue resides in the sb105x driver module which is part of the staging area of the kernel, indicating it was experimental or incomplete code that had not yet undergone full review processes. The mp_get_count function specifically handles the TIOCGICOUNT ioctl command which is designed to retrieve interrupt count information from serial ports. The flaw occurs because the function fails to properly initialize a data structure before populating it with information from kernel memory, creating a situation where uninitialized stack variables contain residual data from previous operations.
This vulnerability falls under the CWE-119 category of "Improper Access to Memory Location" and more specifically relates to CWE-248, "Uncaught Exception," as the lack of proper initialization leads to information leakage rather than a direct crash. The security impact is significant because local users can exploit this weakness to extract sensitive kernel memory contents through the ioctl interface. The TIOCGICOUNT command is typically used by applications to monitor serial port interrupt statistics, but due to the uninitialized data structure, attackers can inadvertently access kernel stack memory containing potentially sensitive information such as cryptographic keys, passwords, or other confidential data that may have previously occupied that memory location.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with potential material for more sophisticated attacks. While the vulnerability requires local access to exploit, it can serve as a stepping stone for privilege escalation attacks or as part of a broader exploitation strategy. The fact that this affected the staging driver component suggests that the vulnerability may have been present for an extended period without detection, as staging drivers typically receive less rigorous security review than mainline kernel components. Attackers could potentially use this information to perform memory analysis attacks, fingerprint kernel versions, or gather intelligence about system configurations that could aid in targeting other vulnerabilities.
Mitigation strategies for CVE-2013-4516 primarily involve upgrading to Linux kernel versions 3.12 or later where the uninitialized data structure issue has been resolved. System administrators should prioritize patching systems running affected kernel versions, particularly those in production environments where local access might be compromised. The fix implemented in the patched version ensures proper initialization of the data structure before it is populated with values, eliminating the information disclosure vector. Organizations should also implement monitoring for unauthorized local access attempts and consider implementing kernel lockdown mechanisms or other security controls that limit local user privileges. From an ATT&CK perspective, this vulnerability maps to T1059.001 (Command and Scripting Interpreter: PowerShell) and T1068 (Exploitation for Privilege Escalation) as it provides a potential information gathering primitive that could be leveraged in more complex attack chains. The vulnerability highlights the importance of proper memory initialization practices in kernel code and demonstrates how seemingly minor initialization oversights can create significant security implications, particularly in the context of kernel-level memory management where data leakage can compromise entire system security postures.