CVE-2012-6547 in Linux
Summary
by MITRE
The __tun_chr_ioctl function in drivers/net/tun.c in the Linux kernel before 3.6 does not initialize a certain structure, which allows local users to obtain sensitive information from kernel stack memory via a crafted application.
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Analysis
by VulDB Data Team • 01/01/2022
The vulnerability identified as CVE-2012-6547 resides within the Linux kernel's TUN/TAP network driver implementation, specifically in the __tun_chr_ioctl function located in drivers/net/tun.c. This flaw represents a classic information disclosure vulnerability that emerged in kernel versions prior to 3.6, affecting systems that utilize the TUN/TAP virtual network interfaces for network packet forwarding and virtualization purposes. The TUN/TAP driver is commonly employed in virtualization environments, containerization platforms, and network security applications where users need to create virtual network interfaces for various networking tasks.
The technical root cause of this vulnerability stems from improper initialization of a structure within the __tun_chr_ioctl function. When a crafted application invokes specific ioctl commands through the TUN/TAP character device interface, the function fails to properly initialize certain data members of an internal structure before using them. This incomplete initialization results in the structure containing residual data from previous operations or stack contents, effectively leaking kernel memory contents to unprivileged userspace applications. The vulnerability is particularly concerning because it operates at the kernel level where sensitive information such as cryptographic keys, passwords, or other confidential data might be present in the memory stack.
The operational impact of CVE-2012-6547 extends beyond simple information disclosure, as local attackers with minimal privileges can exploit this flaw to gain insights into kernel memory layout and potentially extract sensitive data. This vulnerability aligns with CWE-1286, which categorizes improper initialization of structure members as a weakness that can lead to information exposure. The attack vector is particularly dangerous in environments where TUN/TAP interfaces are used for network virtualization or security appliances, as it allows attackers to gather intelligence about the kernel state and potentially aid in more sophisticated attacks. According to ATT&CK framework, this vulnerability maps to T1059.001 (Command and Scripting Interpreter: PowerShell) and T1552.001 (Unsecured Credentials: Credentials in Files) through the information gathering phase, enabling attackers to collect sensitive kernel memory data that could reveal system configuration details or cryptographic material.
Mitigation strategies for CVE-2012-6547 primarily involve upgrading to Linux kernel version 3.6 or later, where the structure initialization issue has been properly addressed. System administrators should also implement proper access controls on TUN/TAP device interfaces, restricting usage to trusted applications and users. Additional defensive measures include monitoring for unusual ioctl activity patterns and implementing kernel hardening techniques such as stack canaries and kernel address space layout randomization. The vulnerability demonstrates the critical importance of proper initialization practices in kernel code and highlights how seemingly minor oversights in memory management can lead to significant security implications. Organizations maintaining legacy systems should prioritize patching this vulnerability as it represents a foundational security issue that could be exploited as a stepping stone for more advanced attacks targeting kernel memory corruption or privilege escalation.