CVE-2016-4485 in Linux
Summary
by MITRE
The llc_cmsg_rcv function in net/llc/af_llc.c in the Linux kernel before 4.5.5 does not initialize a certain data structure, which allows attackers to obtain sensitive information from kernel stack memory by reading a message.
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Analysis
by VulDB Data Team • 08/18/2022
The vulnerability identified as CVE-2016-4485 resides within the Linux kernel's implementation of the Logical Link Control protocol layer, specifically in the llc_cmsg_rcv function located in net/llc/af_llc.c. This flaw represents a classic information disclosure vulnerability that affects kernel versions prior to 4.5.5, creating a significant security risk for systems utilizing the Linux networking stack. The issue manifests when the kernel fails to properly initialize a critical data structure during message processing, leaving sensitive kernel memory contents accessible to unauthorized users.
The technical nature of this vulnerability stems from improper initialization of kernel data structures, which falls under the CWE-457 category of "Use of Uninitialized Variable." When the llc_cmsg_rcv function processes incoming messages, it does not properly clear or initialize certain memory areas that contain kernel stack data. This incomplete initialization allows attackers to read uninitialized memory contents that may include sensitive information such as cryptographic keys, session tokens, system credentials, or other confidential data that was previously stored in the same memory locations. The vulnerability operates at the kernel level, making it particularly dangerous as it bypasses normal user-space security boundaries and directly accesses kernel memory spaces.
From an operational impact perspective, this vulnerability enables attackers to perform kernel memory disclosure attacks that can lead to complete system compromise. An attacker with network access can exploit this vulnerability by sending specially crafted messages to the LLC protocol layer, potentially extracting sensitive kernel memory contents that could be used to reconstruct system state, discover security credentials, or aid in further exploitation attempts. The attack vector is network-based, requiring only that the attacker can communicate with the target system through the LLC protocol, making it particularly concerning for networked systems. This vulnerability can be leveraged as a stepping stone for more sophisticated attacks, as the leaked information often provides crucial insights into kernel memory layout and system internals that can be exploited in subsequent attacks.
The mitigation strategy for CVE-2016-4485 involves immediate patching of affected Linux kernel versions to 4.5.5 or later, where the improper initialization issue has been corrected. System administrators should prioritize updating their kernel versions and verify that the patch has been properly applied. Additionally, network segmentation and access controls should be implemented to limit exposure to potential attackers, although these measures only provide partial protection since the vulnerability exists within the kernel itself. The ATT&CK framework categorizes this vulnerability under T1005 "Data from Local System" and T1059 "Command and Scripting Interpreter" as it enables attackers to extract sensitive data from kernel memory and potentially use that information to execute further malicious activities. Organizations should also implement continuous monitoring for unusual network traffic patterns that might indicate exploitation attempts and maintain up-to-date threat intelligence regarding similar kernel vulnerabilities.