Linux Kernel Vulnerability in SMB Client and Fallocate Handling

CVE-2026-68388

What is CVE-2026-68388?

A vulnerability in the Linux kernel affects the SMB client implementation of the fallocate function, which is used to manipulate file space allocation. When processing overlapping allocated ranges, the function can incorrectly skip portions of file space that should be zero-filled due to a misalignment in its range handling logic. As a result, this flaw can lead to situations where subsequent write operations to these skipped spaces may encounter errors, such as running out of space, despite being allocated. This issue underscores the importance of ensuring accurate range validation to maintain reliable file system operations and data integrity.

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