ksmbd: validate inherited ACE SID length

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Summary

CVECVE-2026-43490
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-15 06:16:20 UTC
Updated2026-05-20 17:16:23 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: ksmbd: validate inherited ACE SID length smb_inherit_dacl() walks the parent directory DACL loaded from the security descriptor xattr. It verifies that each ACE contains the fixed SID header before using it, but does not verify that the variable-length SID described by sid.num_subauth is fully contained in the ACE. A malformed inheritable ACE can advertise more subauthorities than are present in the ACE. compare_sids() may then read past the ACE. smb_set_ace() also clamps the copied destination SID, but used the unchecked source SID count to compute the inherited ACE size. That could advance the temporary inherited ACE buffer pointer and nt_size accounting past the allocated buffer. Fix this by validating the parent ACE SID count and SID length before using the SID during inheritance. Compute the inherited ACE size from the copied SID so the size matches the bounded destination SID. Reject the inherited DACL if size accumulation would overflow smb_acl.size or the security descriptor allocation size.

Risk And Classification

Primary CVSS: v3.1 8.8 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.000250000 probability, percentile 0.076420000 (date 2026-05-28)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary8.8HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED8.8HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 a7fb771314fb3a265d30f8ac245869a367ab065c git Not specified
CNA Linux Linux affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 47c6e37a77b10e74f70d845ba4ea5d3cafa00336 git Not specified
CNA Linux Linux affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 1aa60fea7f637c071f529ad6784aecca2f2f0c5f git Not specified
CNA Linux Linux affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 c1d95c995d5bcb24b639200a899eda59cb1e6d64 git Not specified
CNA Linux Linux affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 996454bc0da84d5a1dedb1a7861823087e01a7ae git Not specified
CNA Linux Linux affected 5.15 Not specified
CNA Linux Linux unaffected 5.15 semver Not specified
CNA Linux Linux unaffected 6.6.141 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.88 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.30 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.7 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1-rc3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/1aa60fea7f637c071f529ad6784aecca2f2f0c5f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a7fb771314fb3a265d30f8ac245869a367ab065c https://git.kernel.org/stable/c/a7fb771314fb3a265d30f8ac245869a367ab065c git.kernel.org
git.kernel.org/stable/c/c1d95c995d5bcb24b639200a899eda59cb1e6d64 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/47c6e37a77b10e74f70d845ba4ea5d3cafa00336 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/996454bc0da84d5a1dedb1a7861823087e01a7ae 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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