CVE-2026-43490 (GCVE-0-2026-43490)

Vulnerability from cvelistv5 – Published: 2026-05-15 05:15 – Updated: 2026-05-20 16:08
VLAI?
Title
ksmbd: validate inherited ACE SID length
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.
Severity ?
8.8 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 47c6e37a77b10e74f70d845ba4ea5d3cafa00336 (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 1aa60fea7f637c071f529ad6784aecca2f2f0c5f (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < c1d95c995d5bcb24b639200a899eda59cb1e6d64 (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 996454bc0da84d5a1dedb1a7861823087e01a7ae (git)
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Linux Linux Affected: 5.15
Unaffected: 0 , < 5.15 (semver)
Unaffected: 6.12.88 , ≤ 6.12.* (semver)
Unaffected: 6.18.30 , ≤ 6.18.* (semver)
Unaffected: 7.0.7 , ≤ 7.0.* (semver)
Unaffected: 7.1-rc3 , ≤ * (original_commit_for_fix)
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{
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          "programFiles": [
            "fs/smb/server/smbacl.c"
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    "dateReserved": "2026-05-01T14:12:56.012Z",
    "dateUpdated": "2026-05-20T16:08:10.161Z",
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  }
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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