CVE-2024-47699 is a vulnerability identified in the Linux kernel's NILFS2 (New Implementation of a Log-structured File System) component, specifically within the nilfs_btree_insert() function. The issue arises when the filesystem's b-tree structure is corrupted, particularly when the b-tree root node has a height greater than 2 but zero child nodes. Under these conditions, a NULL pointer dereference occurs due to the nilfs_btree_do_lookup() function failing to set the block buffer head (bp_bh) for the path structure, leaving it as NULL. Subsequently, nilfs_btree_get_nonroot_node() attempts to access this NULL pointer, leading to a kernel NULL pointer dereference. This can cause the kernel to crash (kernel panic) or potentially be exploited for denial of service. The root cause is a lack of proper sanity checks on the b-tree root node's child count relative to its height. The patch introduces an additional check in nilfs_btree_root_broken() to detect this inconsistency early and prevent the NULL pointer dereference. The vulnerability was discovered through fuzzing efforts by syzbot and clarified by contributor Lizhi Xu. The affected versions are specific Linux kernel commits identified by the hash 17c76b0104e4a6513983777e1a17e0297a12b0c4, indicating a narrow range of affected kernel builds. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations, the primary impact of CVE-2024-47699 is the potential for denial of service (DoS) via kernel crashes on systems running affected Linux kernel versions with NILFS2 filesystems. While NILFS2 is not the most commonly used filesystem in enterprise environments (ext4, XFS, Btrfs are more prevalent), it is used in some specialized or embedded systems. A successful exploitation could cause system instability, leading to downtime, loss of availability, and potential disruption of critical services. In environments where NILFS2 is used for logging or data storage, corrupted filesystem images could trigger this vulnerability, causing unexpected reboots or crashes. Although the vulnerability does not currently have known exploits, the ease of triggering a NULL pointer dereference in kernel space means attackers with local access or the ability to supply corrupted filesystem images could cause service interruptions. This could affect cloud providers, hosting services, or industrial control systems in Europe that rely on Linux systems with NILFS2. Confidentiality and integrity impacts are minimal since this is primarily a stability issue, but availability is significantly affected. Organizations with strict uptime requirements or critical infrastructure should prioritize patching to avoid potential disruptions.

1. Apply the official Linux kernel patch that addresses CVE-2024-47699 as soon as it is available in your distribution's kernel updates. 2. Identify and inventory systems using NILFS2 filesystems, especially those running kernel versions around the affected commit. 3. Avoid using NILFS2 on critical production systems unless necessary, or consider migrating data to more widely supported and tested filesystems like ext4 or XFS. 4. Implement filesystem integrity monitoring to detect corruption early, preventing corrupted b-tree structures from causing kernel crashes. 5. Restrict local access and control the ability to mount or manipulate NILFS2 filesystems to trusted administrators only. 6. Employ kernel crash monitoring and automated recovery mechanisms to minimize downtime in case of unexpected crashes. 7. For embedded or specialized Linux systems, coordinate with vendors to ensure timely patching and firmware updates. 8. Conduct regular backups of data stored on NILFS2 filesystems to enable recovery in case of corruption or crashes.