CVE-2017-6345 in Linux
Summary
by MITRE
The LLC subsystem in the Linux kernel before 4.9.13 does not ensure that a certain destructor exists in required circumstances, which allows local users to cause a denial of service (BUG_ON) or possibly have unspecified other impact via crafted system calls.
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Analysis
by VulDB Data Team • 09/03/2020
The vulnerability identified as CVE-2017-6345 resides within the Linux kernel's LLC (Logical Link Control) subsystem, a component responsible for managing network communication protocols at the data link layer. This flaw affects kernel versions prior to 4.9.13 and represents a critical design oversight that can be exploited by local attackers to disrupt system operations. The LLC subsystem operates as part of the kernel's networking stack, handling communication between network devices and managing connection states through various protocol implementations.
The technical root cause of this vulnerability stems from insufficient validation within the LLC subsystem's destructor functions. Specifically, the kernel fails to guarantee that essential cleanup routines are properly executed under certain conditions when processing crafted system calls. This absence of required destructor functionality creates a scenario where the kernel's BUG_ON macro can be triggered, leading to system crashes and potential denial of service conditions. The vulnerability manifests when maliciously constructed system calls are issued against the LLC subsystem, causing the kernel to encounter an unexpected state that violates internal consistency checks.
From an operational perspective, this vulnerability presents significant risks to system stability and availability. Local attackers with access to the system can exploit this weakness to initiate denial of service attacks that may result in complete system crashes or reboot cycles. The impact extends beyond simple service disruption as the BUG_ON condition can potentially trigger cascading failures within the kernel's memory management and networking subsystems. Additionally, while the primary impact is denial of service, the unspecified other impacts referenced in the vulnerability description suggest potential for more severe consequences including privilege escalation or information disclosure under certain circumstances.
The vulnerability aligns with CWE-691, which addresses insufficient control flow management in kernel components, and represents a classic example of inadequate error handling in kernel space code. From an attack methodology standpoint, this flaw fits within the ATT&CK framework under the technique of privilege escalation through kernel exploits, specifically targeting the kernel's networking subsystem. The local nature of the attack means that exploitation requires system access, but once achieved, the impact can be severe as the attacker can potentially disrupt critical system services or cause complete system instability.
Mitigation strategies for CVE-2017-6345 primarily focus on kernel version updates, with the most effective solution being the deployment of Linux kernel versions 4.9.13 or later where the vulnerability has been addressed. System administrators should prioritize patching affected systems and monitor for any signs of exploitation attempts. Additional defensive measures include implementing kernel hardening techniques such as stack canaries, kernel address space layout randomization, and restricting local user privileges where possible. Network segmentation and monitoring for unusual system call patterns may also help detect potential exploitation attempts, though the local nature of the vulnerability means that comprehensive system access controls remain the most effective preventive approach.