CVE-2015-2041 in Linux
Summary
by MITRE
net/llc/sysctl_net_llc.c in the Linux kernel before 3.19 uses an incorrect data type in a sysctl table, which allows local users to obtain potentially sensitive information from kernel memory or possibly have unspecified other impact by accessing a sysctl entry.
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Analysis
by VulDB Data Team • 03/10/2022
The vulnerability identified as CVE-2015-2041 resides within the Linux kernel's implementation of the LLC (Logical Link Control) subsystem, specifically in the net/llc/sysctl_net_llc.c file. This flaw represents a classic case of improper data type handling within kernel system control interfaces that can lead to information disclosure and potential privilege escalation. The issue manifests when the kernel processes sysctl entries related to LLC configuration parameters, where an incorrect data type is used in the sysctl table structure, creating a mismatch between how data is stored and how it is accessed by userspace applications.
The technical root cause of this vulnerability stems from a type confusion error in the kernel's sysctl implementation where the data type specified for a particular sysctl parameter does not match the actual data type of the underlying kernel variable. This mismatch allows local attackers to manipulate the sysctl interface in ways that can result in kernel memory being read and exposed to userspace processes. The vulnerability is particularly concerning because sysctl interfaces are designed to provide controlled access to kernel parameters, and when these interfaces contain type inconsistencies, they can become vectors for information leakage that might reveal sensitive kernel memory contents including potentially confidential data, cryptographic keys, or other system information that should remain protected within kernel space.
From an operational perspective, this vulnerability enables local users to potentially extract sensitive information from kernel memory through carefully crafted sysctl access attempts. The impact extends beyond simple information disclosure as the incorrect data type handling could potentially lead to unspecified other impacts, including system instability or privilege escalation opportunities. The attack surface is limited to local users who have access to the system, but the potential for exploitation increases when considering that such users might be able to leverage this information to conduct more sophisticated attacks or gain additional system privileges. This vulnerability aligns with CWE-128, which describes "Wrap or Overflow" conditions in data type handling, and can be mapped to ATT&CK technique T1059.003 for execution through system calls, particularly when considering the potential for privilege escalation.
The mitigation strategy for CVE-2015-2041 involves upgrading to Linux kernel versions 3.19 or later, where the sysctl table type mismatch has been corrected. System administrators should prioritize patching affected systems, particularly those running older kernel versions that may be vulnerable to this type of information disclosure. Additionally, organizations should implement monitoring for unusual sysctl access patterns that might indicate exploitation attempts, and consider implementing additional security controls such as capability-based access restrictions for sysctl interfaces. The fix addresses the root cause by ensuring proper data type alignment in the sysctl table structure, preventing the type confusion that enables the information disclosure. Security teams should also conduct vulnerability assessments to identify systems running affected kernel versions and ensure comprehensive patch management processes are in place to prevent similar issues from arising in the future, as this vulnerability demonstrates the critical importance of proper type handling in kernel interfaces.