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CVE-2026-90153NVD
Vulnerability Summary
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size
smb_check_perm_dacl() validates that the DACL fits inside the NT
security descriptor, but then bounds its two ACE walks by the
remaining NTSD length (acl_size) rather than the DACL's declared
size (pdacl_size).
When pdacl->size is smaller than the trailing NTSD buffer, bytes
after the declared DACL boundary - still inside the stored security
descriptor - are parsed as ACEs during access checks. A crafted
DACL can place an access-granting ACE beyond pdacl->size, and the
current code accepts it during SMB2_CREATE access validation, while
parse_dacl() and smb_inherit_dacl() stop at pdacl_size.
Bound both ACE walks by pdacl_size to match the DACL boundary
semantics used elsewhere in the server.
Validation:
- semantic KUnit harness shows the post-boundary ACE is selected
before the fix and rejected (EACCES) after it
- linux master (7.2-rc6), x86_64
ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size
smb_check_perm_dacl() validates that the DACL fits inside the NT
security descriptor, but then bounds its two ACE walks by the
remaining NTSD length (acl_size) rather than the DACL's declared
size (pdacl_size).
When pdacl->size is smaller than the trailing NTSD buffer, bytes
after the declared DACL boundary - still inside the stored security
descriptor - are parsed as ACEs during access checks. A crafted
DACL can place an access-granting ACE beyond pdacl->size, and the
current code accepts it during SMB2_CREATE access validation, while
parse_dacl() and smb_inherit_dacl() stop at pdacl_size.
Bound both ACE walks by pdacl_size to match the DACL boundary
semantics used elsewhere in the server.
Validation:
- semantic KUnit harness shows the post-boundary ACE is selected
before the fix and rejected (EACCES) after it
- linux master (7.2-rc6), x86_64
CVSS v3.1 Base Metrics — Score 8.1 (HIGH)
Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredLow
User InteractionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityNone
Affected & Patched Versions
- Linux Linux >= 8f0541186e9ad1b62accc9519cc2b7a7240272a7 and < a2051ffe452afad52f580b85a3fd8851933b1e7c
- Linux Linux >= 8f0541186e9ad1b62accc9519cc2b7a7240272a7 and < a29f57a14c939586d84d7fd6a029bd1fd170098f
- Linux Linux >= 8f0541186e9ad1b62accc9519cc2b7a7240272a7 and < a4a307d149327dad5fb25187e1b03cebd1b04de6
- Linux Linux >= 8f0541186e9ad1b62accc9519cc2b7a7240272a7 and < 8e4f75e979c1d9a51b0a48ac33d0cfd5f039ec67
- Linux Linux >= 8f0541186e9ad1b62accc9519cc2b7a7240272a7 and < 79decd88dd3f0d42e7fb0689b1a7853bfa302459
- Linux Linux >= cb69d4d6f709f87c94afa28ae64c501576692171
- Linux Linux >= 6e8f4abf584253cbaa596ea4ad13110cf61cd4c9
- Linux Linux >= 8e33102309bd6839b2e2e158f93a7b378cb4655d
- Linux Linux >= 5.15.62 and < 5.16
- Linux Linux >= 5.18.18 and < 5.19
- Linux Linux >= 5.19.2 and < 5.20
- Linux Linux >= 6.0
- Linux Linux a2051ffe452afad52f580b85a3fd8851933b1e7c
- Linux Linux a29f57a14c939586d84d7fd6a029bd1fd170098f
- Linux Linux a4a307d149327dad5fb25187e1b03cebd1b04de6
- Linux Linux 8e4f75e979c1d9a51b0a48ac33d0cfd5f039ec67
- Linux Linux 79decd88dd3f0d42e7fb0689b1a7853bfa302459
- Linux Linux 5.16
- Linux Linux 5.19
- Linux Linux 5.20
External References
- https://git.kernel.org/stable/c/a2051ffe452afad52f580b85a3fd8851933b1e7c
- https://git.kernel.org/stable/c/a29f57a14c939586d84d7fd6a029bd1fd170098f
- https://git.kernel.org/stable/c/a4a307d149327dad5fb25187e1b03cebd1b04de6
- https://git.kernel.org/stable/c/8e4f75e979c1d9a51b0a48ac33d0cfd5f039ec67
- https://git.kernel.org/stable/c/79decd88dd3f0d42e7fb0689b1a7853bfa302459