Linux Kernel up to 7.1.3 ksmbd smb2_ioctl daccess permission

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
4.1	$0-$5k	1.60

Summaryinfo

A vulnerability has been found in Linux Kernel up to 6.1.177/6.6.144/6.12.95/6.18.38/7.1.3 and classified as problematic. This issue affects the function smb2_ioctl of the component ksmbd. Performing a manipulation of the argument daccess results in permission. This vulnerability is identified as CVE-2026-64399. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability classified as problematic has been found in Linux Kernel up to 6.1.177/6.6.144/6.12.95/6.18.38/7.1.3. This affects the function smb2_ioctl of the component ksmbd. The manipulation of the argument daccess with an unknown input leads to a permission vulnerability. CWE is classifying the issue as CWE-275. This is going to have an impact on integrity. The summary by CVE is:

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.

It is possible to read the advisory at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-64399 since 07/19/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 07/25/2026). The attack technique deployed by this issue is T1222 according to MITRE ATT&CK.

Upgrading to version 6.1.178, 6.6.145, 6.12.96, 6.18.39, 7.1.4 or 7.2-rc1 eliminates this vulnerability. Applying the patch bf460ad5958d506492de4524a656439da3f99c51/620d133d469295ee7c017ca6aafac335f65c4a5a/9b9cf7e65cbeaae1b6636144bacee611cdd7a5d6/baae7b39673ec21073a25e3d14f8feaada01d5df/c917e4522d251071dde9871b9142d8ea1186ebfe/388e4139db27a9e3612c9d356b826f5b1ff6a9e3 is able to eliminate this problem.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.1.177
• 6.6.144
• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
• 6.12.5
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• 6.12.92
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• 6.12.94
• 6.12.95
• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
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• 6.18.34
• 6.18.35
• 6.18.36
• 6.18.37
• 6.18.38
• 7.1.0
• 7.1.1
• 7.1.2
• 7.1.3

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.3
VulDB Meta Temp Score: 4.1

VulDB Base Score: 4.3
VulDB Temp Score: 4.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Permission
CWE: CWE-275 / CWE-266
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.1.178/6.6.145/6.12.96/6.18.39/7.1.4/7.2-rc1
Patch: bf460ad5958d506492de4524a656439da3f99c51/620d133d469295ee7c017ca6aafac335f65c4a5a/9b9cf7e65cbeaae1b6636144bacee611cdd7a5d6/baae7b39673ec21073a25e3d14f8feaada01d5df/c917e4522d251071dde9871b9142d8ea1186ebfe/388e4139db27a9e3612c9d356b826f5b1ff6a9e3

Timelineinfo

07/19/2026 CVE reserved
07/25/2026 +6 days Advisory disclosed
07/25/2026 +0 days VulDB entry created
07/25/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-64399 (🔒)
GCVE (CVE): GCVE-0-2026-64399
GCVE (VulDB): GCVE-100-383211

Entryinfo

Created: 07/25/2026 18:31
Changes: 07/25/2026 18:31 (60)
Complete: 🔍
Cache ID: 216::103

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Discussion

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