ksmbd: validate inherited ACE SID length
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-787 and the CVSS impact.
Summary
In 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.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Linux | Linux | 5.15 and later | 6.1.191, 6.6.141, 6.12.88, 6.18.30, 7.0.7, 7.1 | Patch available | CNA |
- Linux VendorLinux Affected 5.15 and later Fixed in 6.1.191, 6.6.141, 6.12.88, 6.18.30, 7.0.7, 7.1 Patch available CNA
CPE configurations NVD · 3
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 5.15 to before 6.6.141; 6.7 to before 6.12.88; 6.13 to before 6.18.30; 6.19 to before 7.0.7 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:* | 7.1 rc1 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:* | 7.1 rc2 | Vulnerable | Linux |
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 5.15 to before 6.6.141; 6.7 to before 6.12.88; 6.13 to before 6.18.30; 6.19 to before 7.0.7 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:* Versions 7.1 rc1 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:* Versions 7.1 rc2 Vulnerable ·Linux
Remediation
- Fix · CNA Linux (Linux) Fixed in 6.1.191, 6.6.141, 6.12.88, 6.18.30, 7.0.7, 7.1
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
Not affected: 5 products
- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
Timeline
- 2026-10-02 Threatist record created from CVE-2026-43490
- 2026-10-03 Alias added: GHSA-9hm7-v4rj-6wqj
- 2026-10-20 Affected versions changed · Red Hat
- 2026-10-30 Fix available: Linux/Linux@00f053d97b63591cafd791dce8d6c53e1625dad1, Linux/[email protected] · CNA
- 2026-10-30 1 new reference · CNA
References
Patch 5
- https://git.kernel.org/stable/c/a7fb771314fb3a265d30f8ac245869a367ab065c
- https://git.kernel.org/stable/c/47c6e37a77b10e74f70d845ba4ea5d3cafa00336
- https://git.kernel.org/stable/c/1aa60fea7f637c071f529ad6784aecca2f2f0c5f
- https://git.kernel.org/stable/c/c1d95c995d5bcb24b639200a899eda59cb1e6d64
- https://git.kernel.org/stable/c/996454bc0da84d5a1dedb1a7861823087e01a7ae
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- TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
- TI-2021-05514 Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE KEVCVSS 3.1HIGH 8.3
Sources
- CVE-2026-43490 · CVE Program
- CVE-2026-43490 · NVD
- FIRST EPSS
- GHSA-9hm7-v4rj-6wqj · GitHub Advisory Database · CC BY 4.0
- CVE-2026-43490 · Red Hat security data · CC BY 4.0
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