Denial-of-Service Vulnerability in Linux Kernel exFAT File System

CVE-2025-40287

What is CVE-2025-40287?

A vulnerability in the Linux kernel's exFAT file system allows an attacker to exploit malformed directory entries, which can lead to an infinite loop and result in a Denial-of-Service condition. Specifically, certain system calls including SYS_openat, SYS_ftruncate, and SYS_pwrite64 can cause the kernel to hang when executed under these conditions. This is due to an improper validation check on the dentry.stream.valid_size parameter during file operations. A patch has been released to add safeguards against negative dentry.stream.valid_size values to mitigate this risk.

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