CVE-2026-64395Network attack vector

File disclosure via unchecked extent-copy source access

Published Jul 25, 2026 · Updated Jul 25, 2026

Improper access control in Linux Kernel ksmbd allows remote attackers to disclose source-file contents through an SMB extent-copy request. FSCTL_DUPLICATE_EXTENTS_TO_FILE passes the source file to vfs_clone_file_range() or vfs_copy_file_range() without verifying FILE_READ_DATA on its handle. Exploitation requires access to open the source with attribute permission and a destination that is readable to the requester; the result is file-content disclosure only.

CVSS severity7.5
High
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in Linux Kernel ksmbd allows remote attackers to disclose source-file contents through an SMB extent-copy request. FSCTL_DUPLICATE_EXTENTS_TO_FILE passes the source file to vfs_clone_file_range() or vfs_copy_file_range() without verifying FILE_READ_DATA on its handle. Exploitation requires access to open the source with attribute permission and a destination that is readable to the requester; the result is file-content disclosure only.

The record

CVE
CVE-2026-64395
Published
Jul 25, 2026
Updated
Jul 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-358, T1005
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <6.1.178
  2. Affected versionversion=0 <6.12.96
  3. Affected versionversion=0 <6.18.39
  4. Affected versionversion=0 <6.6.145
  5. Affected versionversion=0 <7.1.4
  6. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <2d2ab6983620c2d60ce7db72133984ca3873b929
  7. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <67bdad9cf01b25030e3bf00bbce6c309319d6663
  8. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <a10942af27832c2761d020863a46e79bebe0567d
  9. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b0d4d5cb846a1ddb7aaab9adfb5986e4540e6e5f
  10. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <cedff600f1642aa982178503552f0d007bc829c8
  11. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <db231af842868268839f9f9619c68cb27830d8be

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=0 <6.1.178; version=0 <6.12.96; version=0 <6.18.39; version=0 <6.6.145; version=0 <7.1.4; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <2d2ab6983620c2d60ce7db72133984ca3873b929; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <67bdad9cf01b25030e3bf00bbce6c309319d6663; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <a10942af27832c2761d020863a46e79bebe0567d; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b0d4d5cb846a1ddb7aaab9adfb5986e4540e6e5f; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <cedff600f1642aa982178503552f0d007bc829c8; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <db231af842868268839f9f9619c68cb27830d8be

Published CVSS scores

7.5Linux CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-358Improperly Implemented Security Check for Standard
T1005Data from Local System

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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