CVE-2024-56619 is a high-severity vulnerability in the Linux kernel's NILFS2 (New Implementation of a Log-structured File System) component. The flaw arises in the nilfs_find_entry() function, which is responsible for locating directory entries. The root cause is a type mismatch in nilfs_last_byte(), where a 64-bit inode size (i_size) value is assigned to a local variable of type 'unsigned int' instead of 'u64'. This truncation causes the upper 32 bits of the 64-bit size to be lost, leading to an underflow in the calculation of the end address for directory data. Consequently, nilfs_find_entry() may perform out-of-bounds memory accesses beyond the folio or page size. When Kernel Address Sanitizer (KASAN) is enabled, this manifests as a use-after-free bug. The vulnerability can be triggered when the inode's i_size is corrupted and set to a large value, causing the directory search to access invalid memory regions. The fix involves changing the local variable type to 'u64' to preserve the full 64-bit size and prevent bit loss. The return value of nilfs_last_byte() remains 'unsigned int' but is safely truncated to PAGE_SIZE, so no change is needed there. This vulnerability is classified under CWE-416 (Use After Free) and has a CVSS v3.1 score of 7.8, indicating high severity. It requires local privileges (AV:L), low attack complexity (AC:L), and low privileges (PR:L) but no user interaction (UI:N). The impact includes potential full compromise of confidentiality, integrity, and availability of affected systems due to out-of-bounds memory access and use-after-free conditions, which could be exploited for privilege escalation or arbitrary code execution. No known exploits are currently reported in the wild, but the vulnerability is publicly disclosed and patched in recent Linux kernel versions.

For European organizations, this vulnerability poses a significant risk, especially for those relying on Linux-based servers and infrastructure using the NILFS2 filesystem or those with corrupted inode sizes due to hardware faults or software bugs. Exploitation could allow attackers with local access to escalate privileges, execute arbitrary code in kernel context, or cause denial of service via kernel crashes. This could lead to data breaches, service disruptions, and compromise of critical systems. Given the widespread use of Linux in European data centers, cloud providers, and enterprise environments, the vulnerability could affect a broad range of sectors including finance, healthcare, government, and telecommunications. Organizations with multi-tenant environments or shared hosting are particularly at risk if attackers gain local access through other means. The lack of required user interaction facilitates exploitation once local access is obtained. The high impact on confidentiality, integrity, and availability underscores the need for prompt remediation to maintain compliance with European data protection regulations such as GDPR and to protect critical infrastructure.

European organizations should prioritize updating their Linux kernels to the latest patched versions that address CVE-2024-56619. Since the vulnerability requires local access, organizations should also strengthen access controls to limit user privileges and restrict local login capabilities. Implementing strict kernel hardening measures such as enabling Kernel Address Sanitizer (KASAN) in testing environments can help detect similar issues early. Regular integrity checks on filesystem metadata and inode sizes can help identify corruption that might trigger this vulnerability. Employing mandatory access controls (e.g., SELinux, AppArmor) can limit the impact of potential exploitation. For environments where immediate patching is not feasible, consider isolating vulnerable systems and monitoring for unusual kernel crashes or memory errors indicative of exploitation attempts. Additionally, ensure comprehensive logging and alerting on kernel anomalies and privilege escalations. Finally, educate system administrators about the risks of local privilege escalation vulnerabilities and the importance of timely patch management.