CVE-2026-64394Network attack vector

Authenticated file-access escalation via missing handle check

Published Jul 25, 2026 · Updated Jul 25, 2026

Improper authorization in Linux Kernel ksmbd allows remote authenticated users to rewrite file access controls through SMB2 SET_INFO SECURITY. The smb2_set_info_sec() path calls set_info_sec() without checking the handle for WRITE_DAC or WRITE_OWNER before replacing the owner, mode, POSIX ACL, or security-descriptor xattr. A valid SMB session, writable share, and FILE_WRITE_ATTRIBUTES handle are sufficient to grant read, write, or delete access that the handle did not carry.

CVSS severity8.8
High
EPSS probability0.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authorization in Linux Kernel ksmbd allows remote authenticated users to rewrite file access controls through SMB2 SET_INFO SECURITY. The smb2_set_info_sec() path calls set_info_sec() without checking the handle for WRITE_DAC or WRITE_OWNER before replacing the owner, mode, POSIX ACL, or security-descriptor xattr. A valid SMB session, writable share, and FILE_WRITE_ATTRIBUTES handle are sufficient to grant read, write, or delete access that the handle did not carry.

The record

CVE
CVE-2026-64394
Published
Jul 25, 2026
Updated
Jul 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1210
Attack vector
network
Privileges
authenticated

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

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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 <0848b1d8b403f530878195dcbe241a2fddb9d0e1
  7. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <44df157a1183a7f746caa970c169255da5ac61f8
  8. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9ab2ffd3ed3d4ca1667c52de27026ddabc11e537
  9. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <aae600cdaffc6d9ce97645f129799a103a97d06d
  10. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <e6aa731f1b4b3e08caebf66a99f04b22bdab2e99
  11. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <f56535db508ead8dec1c481ad93d7d8acd8f8f1e

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

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 <0848b1d8b403f530878195dcbe241a2fddb9d0e1; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <44df157a1183a7f746caa970c169255da5ac61f8; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9ab2ffd3ed3d4ca1667c52de27026ddabc11e537; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <aae600cdaffc6d9ce97645f129799a103a97d06d; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <e6aa731f1b4b3e08caebf66a99f04b22bdab2e99; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <f56535db508ead8dec1c481ad93d7d8acd8f8f1e

Published CVSS scores

8.8kernel.orgCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1210Exploitation of Remote Services

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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