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VulnerabilityAwaiting classification

CVE-2026-64395

HIGH · 7.5 CVSS v3.1 Developing Published 2026-07-25
No fix yet
No fix has been published. The vendor has not shipped a fixed release or patch. You remain exposed.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click 4 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: ksmbd: require source read access for duplicate extents FSCTL_DUPLICATE_EXTENTS_TO_FILE passes the source file directly to vfs_clone_file_range() or vfs_copy_file_range() without checking the SMB access mask granted to the source handle. A handle opened with attribute access can consequently be used to copy file contents into an attacker-readable destination. Require FILE_READ_DATA on the source handle before either VFS operation, matching other ksmbd data-copy paths.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · low confidence
Developing — this CVE was published recently and its authoritative NVD entry is still being established, so we're holding a technical summary until the source data settles rather than publish something unreliable. Re-checking after 2026-08-08.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Recommended fix Moderate confidence

Any Linux kernel version that includes the ksmbd source code fix for CVE-2026-64395 (the FILE_READ_DATA check before vfs_clone_file_range or vfs_copy_file_range in FSCTL_DUPLICATE_EXTENTS_TO_FILE)

  1. Check current kernel version: uname -r
  2. Identify the distribution and its security advisory channels (e.g., vendor.cve, distro security pages)
  3. For Ubuntu/Debian: Check USN (Ubuntu Security Notices) for corresponding kernel security update
  4. For RHEL/CentOS: Check errata for kernel security advisory
  5. For other distributions: Check distribution-specific security mailing lists or bug trackers
  6. Apply the appropriate kernel security update that includes the ksmbd FILE_READ_DATA check fix
  7. Reboot the system to load the patched kernel
  8. Verify the fix is applied by checking the ksmbd source code for the FILE_READ_DATA check or by confirming the kernel version matches the patched release
Caveat Kernel upgrades may require system reboot and could introduce regressions; test in staging environment first

Generated from the published advisory — verify against the referenced sources before acting.

No vendor fix exists The vendor has not published a patch for this.

There is no version to upgrade to and no patch to apply. Every affected install stays exposed until the vendor ships a fix — or somebody else builds one.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-64395 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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