CVE-2026-64063

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

netfs: Fix streaming write being overwritten

In order to avoid reading whilst writing, netfslib will allow "streaming

writes" in which dirty data is stored directly into folios without reading

them first. Such folios are marked dirty but may not be marked uptodate.

If a folio is entirely written by a streaming write, uptodate will be set,

otherwise it will have a netfs_folio struct attached to ->private recording

the dirty region.

In the event that a partially written streaming write page is to be

overwritten entirely by a single write(), netfs_perform_write() will try to

copy over it, but doesn't discard the netfs_folio if it succeeds; further,

it doesn't correctly handle a partial copy that overwrites some of the

dirty data.

Fix this by the following:

(1) If the folio is successfully overwritten, free the netfs_folio struct

before marking the page uptodate.

(2) If the copy to the folio partially fails,

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References