Linux Kernel up to 7.1.3 ksmbd fs/smb/server/smbacl.c smb2_set_info_sec daccess access control

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.
9.5	$5k-$25k	0.78-

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.1.177/6.6.144/6.12.95/6.18.38/7.1.3. It has been declared as very critical. Affected by this issue is the function smb2_set_info_sec of the file fs/smb/server/smbacl.c of the component ksmbd. Such manipulation of the argument daccess leads to access control. This vulnerability is documented as CVE-2026-64394. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability, which was classified as very critical, has been found in Linux Kernel up to 6.1.177/6.6.144/6.12.95/6.18.38/7.1.3. Affected by this issue is the function smb2_set_info_sec of the file fs/smb/server/smbacl.c of the component ksmbd. The manipulation of the argument daccess with an unknown input leads to a access control vulnerability. Using CWE to declare the problem leads to CWE-284. The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: ksmbd: add a WRITE_DAC/WRITE_OWNER check to SMB2 SET_INFO SECURITY commit cc57232cae23 ("ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE") added a fp->daccess gate to fsctl_set_sparse and noted that "similar handle-level checks exist in other functions but are missing here." The SMB2 SET_INFO SECURITY arm is one of the missing ones, and the most security-relevant: smb2_set_info_sec() calls set_info_sec() with no per-handle access check. set_info_sec() (fs/smb/server/smbacl.c) re-permissions the file: it rewrites owner/group/mode via notify_change(), rewrites the POSIX ACL via set_posix_acl(), and on KSMBD_SHARE_FLAG_ACL_XATTR shares removes and rewrites the Windows security descriptor via ksmbd_vfs_set_sd_xattr(). Every other persistent-mutation arm of the sibling handler smb2_set_info_file() checks fp->daccess first (FILE_WRITE_DATA / FILE_DELETE / FILE_WRITE_EA / FILE_WRITE_ATTRIBUTES); the SECURITY arm — which mutates the access control itself — is the only one with no gate. A client can therefore open a handle with FILE_WRITE_ATTRIBUTES only (no FILE_WRITE_DAC / FILE_WRITE_OWNER) and use SMB2_SET_INFO with InfoType SMB2_O_INFO_SECURITY to rewrite the file's DACL and owner, granting itself access the handle's daccess never carried. Unlike the FSCTL data arms this is a metadata/xattr operation, so there is no FMODE_WRITE VFS backstop — the missing fp->daccess check is the entire gate. Setting a security descriptor is the WRITE_DAC / WRITE_OWNER operation, so require at least one of those on the handle before re-permissioning the file. -EACCES is mapped to STATUS_ACCESS_DENIED by smb2_set_info().

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2026-64394 since 07/19/2026. The exploitation is known to be easy. The attack may be launched remotely. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $5k-$25k at the moment (estimation calculated on 07/25/2026). This vulnerability is assigned to T1068 by the MITRE ATT&CK project.

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 0848b1d8b403f530878195dcbe241a2fddb9d0e1/e6aa731f1b4b3e08caebf66a99f04b22bdab2e99/9ab2ffd3ed3d4ca1667c52de27026ddabc11e537/f56535db508ead8dec1c481ad93d7d8acd8f8f1e/aae600cdaffc6d9ce97645f129799a103a97d06d/44df157a1183a7f746caa970c169255da5ac61f8 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
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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

• 🔒
• 🔒
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CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 9.9
VulDB Meta Temp Score: 9.5

VulDB Base Score: 9.9
VulDB Temp Score: 9.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

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

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Access control
CWE: CWE-284 / 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: 0848b1d8b403f530878195dcbe241a2fddb9d0e1/e6aa731f1b4b3e08caebf66a99f04b22bdab2e99/9ab2ffd3ed3d4ca1667c52de27026ddabc11e537/f56535db508ead8dec1c481ad93d7d8acd8f8f1e/aae600cdaffc6d9ce97645f129799a103a97d06d/44df157a1183a7f746caa970c169255da5ac61f8

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-2026-64394 (🔒)
GCVE (CVE): GCVE-0-2026-64394
GCVE (VulDB): GCVE-100-383186

Entryinfo

Created: 07/25/2026 18:19
Changes: 07/25/2026 18:19 (61)
Complete: 🔍
Cache ID: 216::103

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