CVE-2025-37876 is a vulnerability identified in the Linux kernel related to the netfs filesystem module. The issue arises specifically when the kernel is configured with CONFIG_NETFS_SUPPORTS=y and CONFIG_PROC_FS=n. Under these conditions, the kernel attempts to create the /proc/fs/netfs directory unconditionally, despite the /proc filesystem not being enabled. This leads to a kernel crash due to a NULL pointer dereference or invalid memory access during the initialization of netfs. The crash manifests as a kernel BUG at mm/mempool.c, causing an invalid opcode exception and system panic. The root cause is that the netfs_init() function tries to create the procfs directory without checking if CONFIG_PROC_FS is enabled, violating the expected conditional compilation guards. The fix involves adding an #ifdef guard around the procfs directory creation so that /proc/fs/netfs is only created when CONFIG_PROC_FS is enabled. This vulnerability results in a denial of service (DoS) condition by crashing the kernel during boot or module initialization when the specific kernel configuration is used. It does not appear to allow privilege escalation or code execution directly but can cause system unavailability. The vulnerability affects Linux kernel versions containing the specified commit hashes and is documented as published on May 9, 2025. There are no known exploits in the wild at this time, and no CVSS score has been assigned yet.

For European organizations relying on Linux systems, especially those using custom or minimal kernel configurations that disable procfs (CONFIG_PROC_FS=n) but enable netfs support (CONFIG_NETFS_SUPPORTS=y), this vulnerability can cause critical system instability and denial of service. Systems affected may fail to boot properly or crash unexpectedly, leading to downtime and potential disruption of business operations. This is particularly impactful for embedded Linux devices, specialized appliances, or virtualized environments where custom kernel builds are common. Although the vulnerability does not directly lead to data breaches or privilege escalation, the loss of availability can affect critical infrastructure, cloud services, and enterprise servers running Linux. Organizations in sectors such as telecommunications, manufacturing, and cloud service providers in Europe could face operational risks if their systems are affected. The lack of known exploits reduces immediate risk, but unpatched systems remain vulnerable to accidental crashes or targeted disruption by attackers aware of the configuration specifics.

To mitigate this vulnerability, European organizations should: 1) Audit their Linux kernel configurations to identify if CONFIG_NETFS_SUPPORTS=y is enabled alongside CONFIG_PROC_FS=n. 2) Apply the official Linux kernel patches that add the necessary conditional compilation guards to netfs_init(), ensuring /proc/fs/netfs is only created when procfs is enabled. 3) Rebuild and redeploy affected kernels with the patch applied, especially for custom or embedded Linux distributions. 4) For environments where kernel recompilation is not feasible, consider disabling netfs support if it is not required. 5) Implement monitoring to detect kernel panics or crashes related to mempool allocation or netfs initialization. 6) Test kernel updates in staging environments to verify stability before production deployment. 7) Maintain up-to-date Linux kernel versions and subscribe to vendor security advisories for timely patching. These steps go beyond generic advice by focusing on configuration auditing and targeted patch application relevant to this specific vulnerability.