CVE-2026-68097

ksmbd: validate ACE size against SID sub-authorities

Published Aug 10, 2026 CVSS 3.1 · 8.8 High EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

ksmbd: validate ACE size against SID sub-authorities

set_ntacl_dacl() validates sid.num_subauth before copying an ACE, but
does not verify that the declared ACE size contains all sub-authorities
described by that field. An undersized ACE can therefore be copied
and later make the POSIX ACL deduplication walk inspect data beyond
the copied ACE boundary.

The existing initial bound check is also too small. It only ensures
that the ACE size field is accessible before set_ntacl_dacl() reads
sid.num_subauth farther into the input buffer.

Require enough input for the fixed SID header before accessing
num_subauth, reject ACEs smaller than that header, and skip ACEs
whose declared size cannot contain the complete SID. This makes the
validation consistent with the other ACE walk paths.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4745-1 linux-6.12 security update
Debian DLA Debian DLA DLA-4841-1 linux security update
Ubuntu USN Ubuntu USN USN-8887-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8888-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8889-1 Linux kernel (OEM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8887-2 Linux kernel (AWS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8888-2 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8887-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8917-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8918-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9003-1 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9024-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9025-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9026-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9040-1 Linux kernel (Low Latency NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9043-1 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9066-1 Linux kernel (HWE) vulnerabilities
History
Type Values Removed Values Added
Weaknesses CWE-119
Type Values Removed Values Added
Weaknesses CWE-20
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 8.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
Weaknesses CWE-20
Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate ACE size against SID sub-authorities set_ntacl_dacl() validates sid.num_subauth before copying an ACE, but does not verify that the declared ACE size contains all sub-authorities described by that field. An undersized ACE can therefore be copied and later make the POSIX ACL deduplication walk inspect data beyond the copied ACE boundary. The existing initial bound check is also too small. It only ensures that the ACE size field is accessible before set_ntacl_dacl() reads sid.num_subauth farther into the input buffer. Require enough input for the fixed SID header before accessing num_subauth, reject ACEs smaller than that header, and skip ACEs whose declared size cannot contain the complete SID. This makes the validation consistent with the other ACE walk paths.
Title ksmbd: validate ACE size against SID sub-authorities
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 3, 2026, 10:55 AM
Reserved
Jul 30, 2026, 9:28 AM
Status
Received
Published
Aug 10, 2026, 1:19 PM
Modified
Oct 3, 2026, 11:17 AM