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CVE-2026-64399— ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel 5.15版本存在安全漏洞，该漏洞源于ksmbd的FSCTL_DUPLICATE_EXTENTS_TO_FILE操作缺少权限检查，可能导致客户端覆盖目标文件数据。

CVSS 9.8 · Critical EPSS 0.49% · P41

Affected Version Matrix 14

VendorProduct Version RangeStatus
Linux Linux eb817368f50c1cbe1bd07044124aad7db6330e3a< bf460ad5958d506492de4524a656439da3f99c51 affected
eb817368f50c1cbe1bd07044124aad7db6330e3a< 620d133d469295ee7c017ca6aafac335f65c4a5a affected
eb817368f50c1cbe1bd07044124aad7db6330e3a< 9b9cf7e65cbeaae1b6636144bacee611cdd7a5d6 affected
eb817368f50c1cbe1bd07044124aad7db6330e3a< baae7b39673ec21073a25e3d14f8feaada01d5df affected
eb817368f50c1cbe1bd07044124aad7db6330e3a< c917e4522d251071dde9871b9142d8ea1186ebfe affected
eb817368f50c1cbe1bd07044124aad7db6330e3a< 388e4139db27a9e3612c9d356b826f5b1ff6a9e3 affected
5.15 affected
< 5.15 unaffected
… +6 more rows
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I. Basic Information for CVE-2026-64399

Vulnerability Information
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Vulnerability Title
ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE The FSCTL_DUPLICATE_EXTENTS_TO_FILE arm of smb2_ioctl() overwrites the destination file's data via vfs_clone_file_range() with neither the share-level KSMBD_TREE_CONN_FLAG_WRITABLE check nor a per-handle fp->daccess check that the other write-bearing arms carry. A client can overwrite destination data on a read-only share, or from a handle opened with only FILE_WRITE_ATTRIBUTES (which still yields an FMODE_WRITE filp). FILE_WRITE_ATTRIBUTES-only destination handle overwrote the file's data via the clone. Add both checks, matching the FSCTL_SET_SPARSE permission fix; require FILE_WRITE_DATA since this writes data.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel 5.15版本存在安全漏洞，该漏洞源于ksmbd的FSCTL_DUPLICATE_EXTENTS_TO_FILE操作缺少权限检查，可能导致客户端覆盖目标文件数据。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux eb817368f50c1cbe1bd07044124aad7db6330e3a ~ bf460ad5958d506492de4524a656439da3f99c51 -
Linux Linux 5.15 -

II. Public POCs for CVE-2026-64399

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III. Intelligence Information for CVE-2026-64399

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Patches & Fixes for CVE-2026-64399 (5)

Same Patch Batch · Linux · 2026-07-25 · 274 CVEs total

CVE-2026-64355 9.8 CRITICAL bpf: Reject fragmented frames in devmap
CVE-2026-64410 9.8 CRITICAL netfilter: flowtable: IPIP tunnel hardware offload is not yet support
CVE-2026-64397 9.8 CRITICAL ksmbd: serialize QUERY_DIRECTORY requests per file
CVE-2026-64391 9.8 CRITICAL ksmbd: use opener credentials for ADS I/O
CVE-2026-64387 9.8 CRITICAL smb: client: fix query directory replay double-free
CVE-2026-64386 9.8 CRITICAL smb: client: fix query_info() replay double-free
CVE-2026-64385 9.8 CRITICAL smb: client: fix double-free in SMB2_ioctl() replay
CVE-2026-64383 9.8 CRITICAL smb: client: fix double-free in SMB2_flush() replay
CVE-2026-64384 9.8 CRITICAL smb: client: fix change notify replay double-free
CVE-2026-64268 9.8 CRITICAL RDMA/siw: bound Read Response placement to the RREAD length
CVE-2026-64439 9.8 CRITICAL crypto: krb5 - filter out async aead implementations at alloc
CVE-2026-64303 9.8 CRITICAL spi: fsl-lpspi: terminate the RX channel on TX prepare failure path
CVE-2026-64459 9.8 CRITICAL tcp: restore RCU grace period in tcp_ao_destroy_sock
CVE-2026-64523 9.8 CRITICAL net/handshake: Take a long-lived file reference at submit
CVE-2026-64392 9.1 CRITICAL ksmbd: use opener credentials for delete-on-close
CVE-2026-64319 9.1 CRITICAL nvmet-auth: validate reply message payload bounds against transfer length
CVE-2026-64269 9.1 CRITICAL RDMA/rtrs-srv: Bound RDMA-Write length to chunk size in rdma_write_sg
CVE-2026-64450 9.1 CRITICAL tipc: fix out-of-bounds read in broadcast Gap ACK blocks
CVE-2026-64393 9.1 CRITICAL ksmbd: run set info with opener credentials
CVE-2026-64257 9.1 CRITICAL smb: client: reject overlapping data areas in SMB2 responses

Showing top 20 of 274 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-64399

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