Authenticated access-control bypass via out-of-bounds ACE parsing
Published Sep 17, 2026 · Updated Sep 18, 2026
Improper access control in Linux ksmbd allows remote authenticated users to bypass file permissions via a crafted DACL. smb_check_perm_dacl() bounds both ACE walks by the remaining NT security descriptor length instead of the DACL's declared size, so SMB2_CREATE accepts an access-granting ACE placed after the DACL boundary. Exploitation requires an authenticated SMB session and can grant file access that the declared DACL should deny, without a reported availability impact.
Summary
What happened
Improper access control in Linux ksmbd allows remote authenticated users to bypass file permissions via a crafted DACL. smb_check_perm_dacl() bounds both ACE walks by the remaining NT security descriptor length instead of the DACL's declared size, so SMB2_CREATE accepts an access-granting ACE placed after the DACL boundary. Exploitation requires an authenticated SMB session and can grant file access that the declared DACL should deny, without a reported availability impact.
The record
- CVE
- CVE-2026-90153
- Published
- Sep 17, 2026
- Updated
- Sep 18, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1190
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Sep 17, 2026CVE publishedPublication date reported by the CVE source.
- Sep 18, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=5.15.62 <5.16
- Affected versionversion=5.18.18 <5.19
- Affected versionversion=5.19.2 <5.20
- Affected versionversion=6.0
- Affected versionversion=6e8f4abf584253cbaa596ea4ad13110cf61cd4c9
- Affected versionversion=8e33102309bd6839b2e2e158f93a7b378cb4655d
- Affected versionversion=8f0541186e9ad1b62accc9519cc2b7a7240272a7 <79decd88dd3f0d42e7fb0689b1a7853bfa302459
- Affected versionversion=8f0541186e9ad1b62accc9519cc2b7a7240272a7 <8e4f75e979c1d9a51b0a48ac33d0cfd5f039ec67
- Affected versionversion=8f0541186e9ad1b62accc9519cc2b7a7240272a7 <a2051ffe452afad52f580b85a3fd8851933b1e7c
- Affected versionversion=8f0541186e9ad1b62accc9519cc2b7a7240272a7 <a29f57a14c939586d84d7fd6a029bd1fd170098f
- Affected versionversion=8f0541186e9ad1b62accc9519cc2b7a7240272a7 <a4a307d149327dad5fb25187e1b03cebd1b04de6
- Affected versionversion=cb69d4d6f709f87c94afa28ae64c501576692171
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
Public exploit references
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