In the Linux kernel, the following vulnerability has been resolved: smb: client: discard post-EOF pagecache when extending a file via zero range… (CVE-2026-98686)

The vulnerability in the Linux kernel SMB client related to the smb3_zero_range() function, which previously removed the pagecache only for the zeroed range. When a file was extended, the folio overlapping the old EOF—potentially containing data dirtied past EOF through mmap—was not discarded. This stale data became visible as part of the file content after extension. The fix involved lowering the discard boundary to the smaller of the zero-range offset and the old EOF to ensure that post-EOF pagecache is properly discarded.

This vulnerability could lead to exposure of stale or unintended data beyond the original EOF when a file is extended via zero range operations over SMB. This may result in information disclosure of data that should not be accessible through the file content.

A fix has been applied in the Linux kernel to address this issue by properly discarding the post-EOF pagecache when extending files via zero range. Users should update to the fixed kernel version once available. Patch status is not yet confirmed from vendor advisory; verify with official Linux kernel release notes for the specific patch version.