CVE-2025-37818 is a vulnerability identified in the Linux kernel specifically affecting the LoongArch architecture's memory management subsystem. The issue arises in the huge_pte_offset() function, which is responsible for returning a pointer to a Page Middle Directory (PMD) slot when handling huge page table entries. In the vulnerable versions, huge_pte_offset() returns a pointer even when the PMD entry is invalid and points to invalid_pte_table, indicating no valid mapping. This leads to subsequent kernel functions, such as smaps_hugetlb_range(), fetching an invalid entry value that points to invalid_pte_table. The generic is_swap_pte() check then misinterprets this invalid pointer as a swap entry because it meets the conditions "!pte_present() && !pte_none()". Additionally, is_migration_entry() coincidentally matches the address bits, which causes kernel crashes in the pfn_swap_entry_to_page() function. The root cause is the lack of validation of the PMD entry's content before returning the pointer. The fix involves modifying huge_pte_offset() to verify the PMD entry using pmd_none() and return NULL if the entry is invalid, preventing the kernel from dereferencing invalid pointers and crashing. This vulnerability is architecture-specific to LoongArch and affects certain Linux kernel versions identified by the commit hash fa96b57c149061f71a70bd6582d995f6424fbbf4. No known exploits are reported in the wild as of the publication date (May 8, 2025), and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2025-37818 depends largely on the deployment of Linux systems running on the LoongArch architecture. While LoongArch is a relatively new and less widespread CPU architecture compared to x86 or ARM, its adoption may grow in specialized environments or in organizations experimenting with alternative architectures for performance or security reasons. The vulnerability can cause kernel crashes leading to denial of service (DoS) conditions, potentially disrupting critical services or applications running on affected Linux systems. This could affect availability and operational continuity, especially in data centers or cloud environments using LoongArch-based servers. Although the vulnerability does not directly expose confidentiality or integrity risks, repeated crashes or DoS could indirectly impact business operations and service reliability. Since the flaw is in the kernel's memory management, it could also complicate debugging and recovery efforts. European organizations with research or development environments, or those using LoongArch in embedded or edge devices, should be particularly cautious. The lack of known exploits reduces immediate risk, but the vulnerability should be addressed proactively to prevent future exploitation and maintain system stability.

To mitigate CVE-2025-37818, organizations should prioritize updating their Linux kernels to versions that include the patch fixing huge_pte_offset() behavior on LoongArch. Since the fix involves returning NULL for invalid PMD entries, applying the official kernel update will prevent kernel crashes caused by dereferencing invalid pointers. Organizations should: 1) Identify all Linux systems running on LoongArch architecture within their infrastructure. 2) Verify kernel versions and apply vendor-provided patches or updated kernel releases containing the fix referenced by commit fa96b57c149061f71a70bd6582d995f6424fbbf4. 3) For systems where immediate patching is not feasible, consider isolating or limiting workloads to reduce exposure. 4) Monitor kernel logs and system stability for signs of crashes related to memory management or huge page handling. 5) Engage with Linux distribution vendors or maintainers to ensure timely updates and backports for affected versions. 6) Incorporate this vulnerability into vulnerability management and patching cycles, emphasizing architecture-specific risks. 7) For development or testing environments, validate kernel behavior post-patching to confirm resolution. These steps go beyond generic advice by focusing on architecture-specific identification, patch management, and operational monitoring tailored to LoongArch Linux deployments.