CVE-2012-6538 in Linux
Summary
by MITRE
The copy_to_user_auth function in net/xfrm/xfrm_user.c in the Linux kernel before 3.6 uses an incorrect C library function for copying a string, which allows local users to obtain sensitive information from kernel heap memory by leveraging the CAP_NET_ADMIN capability.
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Analysis
by VulDB Data Team • 01/01/2022
The vulnerability identified as CVE-2012-6538 resides within the Linux kernel's implementation of the xfrm_user subsystem, specifically in the copy_to_user_auth function located in net/xfrm/xfrm_user.c. This flaw represents a classic information disclosure vulnerability that arises from improper handling of memory copying operations between kernel and user space contexts. The vulnerability affects Linux kernel versions prior to 3.6, making it a significant concern for systems running older kernel versions that remain in production environments.
The technical root cause of this vulnerability stems from the misuse of C library functions during kernel space string copying operations. When the copy_to_user_auth function processes user requests, it incorrectly employs a kernel function that does not properly handle the memory boundaries between kernel heap space and user space. This improper function selection leads to a situation where kernel memory contents may be inadvertently exposed to user processes that possess the CAP_NET_ADMIN capability. The CAP_NET_ADMIN capability represents a powerful privilege within the Linux security model, typically granted to network administration processes and system utilities that require extensive network configuration permissions.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides local attackers with access to sensitive kernel heap data that could contain confidential information such as cryptographic keys, session tokens, or other privileged data structures. Attackers with the CAP_NET_ADMIN capability can exploit this flaw to extract kernel memory contents through crafted network configuration requests, potentially leading to privilege escalation or further exploitation of the system. This vulnerability particularly affects systems where network administration processes run with elevated privileges, as the attacker only needs to possess the specific capability rather than full root access to exploit the vulnerability.
From a cybersecurity perspective, this vulnerability aligns with CWE-248, which addresses "Uncaught Exception" in software systems, and represents a memory safety issue that violates fundamental principles of kernel security design. The ATT&CK framework categorizes this vulnerability under T1068, "Exploitation for Privilege Escalation," as local users with CAP_NET_ADMIN can leverage this flaw to gain access to privileged kernel memory. The vulnerability also demonstrates poor input validation and memory management practices that could expose systems to more sophisticated attacks if combined with other exploitation techniques. Organizations should implement immediate patching strategies to address this vulnerability, as the exploitation requires minimal privileges and provides substantial information disclosure capabilities that could serve as a foundation for more advanced attacks. The fix involves correcting the memory copying function calls to properly handle kernel-user space boundaries, ensuring that sensitive kernel heap contents remain protected from unauthorized access by processes with only the CAP_NET_ADMIN capability.