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CVE-2026-43490— ksmbd: validate inherited ACE SID length

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于ksmbd在smb_inherit_dacl()中未验证继承ACE的SID长度，导致恶意可继承ACE可能声明比实际更多的子授权，compare_sids()可能读取超出ACE范围，smb_set_ace()使用未检查的源SID计数计算继承ACE大小，可能导致临时继承ACE缓冲区指针和nt_size计数超出分配缓冲区。

CVSS 8.8 · High EPSS 0.60% · P48

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 12

VendorProduct Version RangeStatus
Linux Linux e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< a7fb771314fb3a265d30f8ac245869a367ab065c affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 47c6e37a77b10e74f70d845ba4ea5d3cafa00336 affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 1aa60fea7f637c071f529ad6784aecca2f2f0c5f affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< c1d95c995d5bcb24b639200a899eda59cb1e6d64 affected
e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9< 996454bc0da84d5a1dedb1a7861823087e01a7ae affected
5.15 affected
< 5.15 unaffected
6.6.141≤ 6.6.* unaffected
… +4 more rows
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I. Basic Information for CVE-2026-43490

Vulnerability Information
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Vulnerability Title
ksmbd: validate inherited ACE SID length
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于ksmbd在smb_inherit_dacl()中未验证继承ACE的SID长度，导致恶意可继承ACE可能声明比实际更多的子授权，compare_sids()可能读取超出ACE范围，smb_set_ace()使用未检查的源SID计数计算继承ACE大小，可能导致临时继承ACE缓冲区指针和nt_size计数超出分配缓冲区。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 ~ a7fb771314fb3a265d30f8ac245869a367ab065c -
Linux Linux 5.15 -

II. Public POCs for CVE-2026-43490

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III. Intelligence Information for CVE-2026-43490

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Patches & Fixes for CVE-2026-43490 (5)

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-43490

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