Refcount Leak Vulnerability in Linux Kernel NFS Services

CVE-2025-40212

What is CVE-2025-40212?

A vulnerability in the Linux kernel's NFSd (Network File System daemon) allows improper handling of filehandles, particularly from NFSv3 clients. When a v3 client interacts with a pseudo root filesystem and uses an invalid filehandle, an error is reported, but the system incorrectly retains a reference. This leads to a potential use-after-free condition when the reference is later dropped, risking a denial of service. The vulnerability can only be exploited under specific conditions, emphasizing the need for proper error handling in filesystem interactions.

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