Bug 2506830 (CVE-2026-64216)

Summary: CVE-2026-64216 kernel: Kernel: netfs Use-After-Free vulnerability allows local denial of service and memory corruption
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerability-draftAssignee: Product Security <prodsec-ir-bot>
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Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the `netfs` component of the Linux kernel. A local user, by interacting with a mounted `netfs` filesystem, could trigger a Use-After-Free (UAF) vulnerability. This flaw occurs when the system attempts to unlock abandoned read pages, potentially leading to a kernel crash and a denial of service. In some cases, this could also result in memory corruption, allowing for information disclosure or data manipulation.
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Description OSIDB Bzimport 2026-07-24 16:07:09 UTC 
In the Linux kernel, the following vulnerability has been resolved:

netfs: Fix potential UAF in netfs_unlock_abandoned_read_pages()

netfs_unlock_abandoned_read_pages(rreq) accesses the index of the folios it
is wanting to unlock and compares that to rreq->no_unlock_folio so that it
doesn't unlock a folio being read for netfs_perform_write() or
netfs_write_begin().

However, given that netfs_unlock_abandoned_read_pages() is called _after_
NETFS_RREQ_IN_PROGRESS is cleared, the one folio that it's not allowed to
dereference is the one specified by ->no_unlock_folio as ownership
immediately reverts to the caller.

Fix this by storing the folio pointer instead and using that rather than
the index.  Also fix netfs_unlock_read_folio() where the same applies.
Comment 1 Mauro Matteo Cascella 2026-07-28 12:50:22 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026072415-CVE-2026-64216-bc28@gregkh/T