CVE-2024-42105 is a vulnerability identified in the Linux kernel's NILFS2 (New Implementation of a Log-structured File System) component. The issue arises from improper validation of the 'ns_first_ino' parameter, which defines the first non-reserved inode number in the filesystem's superblock. Specifically, the vulnerability involves insufficient lower bound checks on 'ns_first_ino', allowing it to be set to values overlapping with reserved inode ranges such as the root directory or metadata files. This misconfiguration leads to malfunctioning of inode number test macros (NILFS_MDT_INODE and NILFS_VALID_INODE) that rely on bit-shift operations. Since these macros use the inode number as the shift count in bitwise operations, setting 'ns_first_ino' to a large or invalid value can cause undefined behavior due to shifts exceeding the integer bit width, which is undefined in C. This can result in logical errors or memory corruption. Additionally, the vulnerability includes a use-after-free condition detected by syzbot, where the internal inode structure is exposed in the namespace on a corrupted filesystem, potentially leading to memory safety issues. The patch series addressing this vulnerability includes proper lower bound checks on 'ns_first_ino', prevention of invalid bit-shift operations, and changing the type of 'ns_first_ino' from signed to unsigned integer to avoid unsafe type casting. The vulnerability affects certain Linux kernel versions identified by specific commit hashes and was published on July 30, 2024. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2024-42105 can be significant, especially for those relying on Linux systems with NILFS2 filesystems. The vulnerability could lead to memory corruption or use-after-free conditions, potentially allowing local attackers or processes with filesystem access to cause system instability, crashes, or even privilege escalation if exploited. This could compromise system availability and integrity, affecting critical infrastructure, servers, or embedded devices running Linux with NILFS2. Although exploitation requires a corrupted filesystem or manipulation of the superblock, environments with high filesystem interaction or where untrusted users have some level of access could be at risk. The exposure of internal inode structures might also facilitate further attacks or information disclosure. Given the widespread use of Linux in European data centers, cloud environments, and industrial control systems, the vulnerability poses a risk to confidentiality, integrity, and availability of systems if left unpatched. However, the lack of known exploits and the complexity of triggering the vulnerability somewhat mitigate immediate risk.

European organizations should prioritize applying the official Linux kernel patches that fix this vulnerability as soon as they become available. Specifically, updating to kernel versions that include the patch series addressing 'ns_first_ino' validation and inode test macro corrections is critical. Organizations should audit systems using NILFS2 filesystems to verify if they are running affected kernel versions and consider migrating critical data to more commonly used and actively maintained filesystems if feasible. Implementing strict access controls to limit who can mount or manipulate filesystems can reduce the risk of exploitation. Additionally, regular filesystem integrity checks and monitoring for filesystem corruption can help detect early signs of exploitation attempts. For environments where NILFS2 is essential, deploying kernel hardening techniques such as memory protection features (e.g., KASLR, SMEP, SMAP) and enabling kernel lockdown modes can further reduce exploitation likelihood. Finally, organizations should maintain robust backup and recovery procedures to mitigate potential data loss or system downtime resulting from exploitation.