CVE-2024-36891 is a vulnerability identified in the Linux kernel's maple_tree data structure implementation, specifically within the mas_empty_area_rev() function. The maple_tree is a data structure used in the kernel to manage virtual memory areas (VMAs). The vulnerability arises because the function mas_start() can return a maple state node pointer that is NULL. Subsequently, mas_data_end() is called assuming the node is valid, leading to a null pointer dereference when it attempts to access information from this NULL node. This results in a kernel oops, effectively causing a denial of service (DoS) by crashing the kernel. The vulnerability can be triggered by a local user who unmaps all VMAs to create an empty maple tree and then maps a new VMA that triggers the problematic code path. The root cause is a logic flaw in handling the maple state transitions and offset settings without verifying the node pointer's validity. The patch involves deferring the offset setting until after confirming the maple state is not empty or single-entry, thereby avoiding dereferencing a NULL pointer. Although no known exploits are reported in the wild, the vulnerability allows a local attacker to cause a kernel crash, impacting system stability and availability. Since it requires local access and specific memory management operations, exploitation complexity is moderate but feasible on systems running vulnerable Linux kernel versions.

For European organizations, this vulnerability poses a risk primarily to system availability and stability. Servers, workstations, and embedded devices running affected Linux kernel versions could be subjected to denial of service attacks by local users or malicious insiders. This could disrupt critical services, especially in environments relying heavily on Linux-based infrastructure such as cloud providers, telecom operators, financial institutions, and public sector organizations. The inability to maintain uptime could lead to operational downtime, loss of productivity, and potential cascading effects on dependent systems. While the vulnerability does not directly compromise confidentiality or integrity, the forced kernel crashes could be leveraged as part of a broader attack chain or to facilitate privilege escalation attempts. Organizations with multi-tenant environments or shared hosting platforms may face increased risk if untrusted users have local access. The absence of known exploits reduces immediate threat but does not eliminate the risk, especially as the vulnerability is publicly disclosed and patches are available. Timely patching is critical to prevent exploitation and maintain service continuity.

1. Apply the official Linux kernel patches that address CVE-2024-36891 as soon as they are released and tested for compatibility with your environment. 2. Implement strict access controls to limit local user privileges, reducing the risk of unprivileged users triggering the vulnerability. 3. Monitor kernel logs and system stability metrics for signs of unexpected kernel oops or crashes that could indicate attempted exploitation. 4. Employ kernel hardening techniques such as SELinux or AppArmor to restrict memory management operations by untrusted processes. 5. Use virtualization or containerization to isolate critical workloads, minimizing the impact of a kernel crash on the overall system. 6. Maintain an up-to-date inventory of Linux kernel versions deployed across your infrastructure to quickly identify and remediate vulnerable systems. 7. Educate system administrators and security teams about this vulnerability to ensure awareness and prompt response to related incidents.