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CVE-2026-64388— smb/client: fix chown/chgrp with SMB3 POSIX Extensions

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 4.18版本存在安全漏洞，该漏洞源于在SMB3 POSIX扩展挂载时对chown/chgrp操作未正确检查posix_extensions，导致所有权和组修改被忽略，影响文件权限管理。

CVSS 7.8 · High EPSS 0.13% · P2

Possible ATT&CK Techniques 1 AI

T1548.002 · Bypass User Account Control

Affected Version Matrix 8

VendorProduct Version RangeStatus
Linux Linux b326614ea2159ea5c835d320f261d05d080cd201< 3eaec47518e126e6dcd1a48521d740278073f0ec affected
b326614ea2159ea5c835d320f261d05d080cd201< 550cfb8a81181331d4d0f76ab75ee58a0bf41e3e affected
b326614ea2159ea5c835d320f261d05d080cd201< 760ef2c579c2609cf17fb1cd5392f64d42d43d33 affected
4.18 affected
< 4.18 unaffected
6.18.57≤ 6.18.* unaffected
7.1.4≤ 7.1.* unaffected
7.2≤ * unaffected
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I. Basic Information for CVE-2026-64388

Vulnerability Information
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Vulnerability Title
smb/client: fix chown/chgrp with SMB3 POSIX Extensions
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: smb/client: fix chown/chgrp with SMB3 POSIX Extensions Ownership (chown) and group (chgrp) modifications were being ignored when mounting with SMB3 POSIX Extensions unless CIFS_MOUNT_CIFS_ACL or CIFS_MOUNT_MODE_FROM_SID were also explicitly set. Fix this by checking for posix_extensions in cifs_setattr_nounix() when updating UID and GID, ensuring that id_mode_to_cifs_acl() is called to map and set the ownership/group information on the server.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/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 4.18版本存在安全漏洞，该漏洞源于在SMB3 POSIX扩展挂载时对chown/chgrp操作未正确检查posix_extensions，导致所有权和组修改被忽略，影响文件权限管理。
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 b326614ea2159ea5c835d320f261d05d080cd201 ~ 3eaec47518e126e6dcd1a48521d740278073f0ec -
Linux Linux 4.18 -

II. Public POCs for CVE-2026-64388

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III. Intelligence Information for CVE-2026-64388

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Patches & Fixes for CVE-2026-64388 (2)

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-2026-64399 9.8 CRITICAL ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE
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-2026-64523 9.8 CRITICAL net/handshake: Take a long-lived file reference at submit
CVE-2026-64459 9.8 CRITICAL tcp: restore RCU grace period in tcp_ao_destroy_sock
CVE-2026-64393 9.1 CRITICAL ksmbd: run set info with opener credentials
CVE-2026-64269 9.1 CRITICAL RDMA/rtrs-srv: Bound RDMA-Write length to chunk size in rdma_write_sg
CVE-2026-64392 9.1 CRITICAL ksmbd: use opener credentials for delete-on-close
CVE-2026-64450 9.1 CRITICAL tipc: fix out-of-bounds read in broadcast Gap ACK blocks
CVE-2026-64320 9.1 CRITICAL nvmet: fix pre-auth out-of-bounds heap read in Discovery Get Log Page

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-2026-64388

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