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Review reviewHigh

CVE-2026-64394

Linux

In the Linux kernel, the following vulnerability has been resolved: ksmbd: add a WRITE_DAC/WRITE_OWNER check to SMB2 SET_INFO SECURITY commit cc57232cae23 ("ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE") added a fp->daccess gate to fsctl_set_sparse and noted that "similar handle-level checks exist in other functions but are missing here." The SMB2 SET_INFO SECURITY arm is one of the missing ones, and the most security-relevant: smb2_set_info_sec() calls set_info_sec() with no per-handle access check. set_info_sec() (fs/smb/server/smbacl.c) re-permissi...

CVSS
8.8
EPSS
-
- percentile
CISA KEV
Not listed
Published
2026.07.25
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability-
Technical severityCVSS 8.8

Vulnerability overview

In the Linux kernel, the following vulnerability has been resolved: ksmbd: add a WRITE_DAC/WRITE_OWNER check to SMB2 SET_INFO SECURITY commit cc57232cae23 ("ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE") added a fp->daccess gate to fsctl_set_sparse and noted that "similar handle-level checks exist in other functions but are missing here." The SMB2 SET_INFO SECURITY arm is one of the missing ones, and the most security-relevant: smb2_set_info_sec() calls set_info_sec() with no per-handle access check. set_info_sec() (fs/smb/server/smbacl.c) re-permissi...

Affected product and versions

Product
Linux
Affected versions
>= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < 0848b1d8b403f530878195dcbe241a2fddb9d0e1, >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < e6aa731f1b4b3e08caebf66a99f04b22bdab2e99, >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < 9ab2ffd3ed3d4ca1667c52de27026ddabc11e537, >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < f56535db508ead8dec1c481ad93d7d8acd8f8f1e, >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < aae600cdaffc6d9ce97645f129799a103a97d06d, >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 < 44df157a1183a7f746caa970c169255da5ac61f8, >= 5.15
Fixed versions
No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Linux and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
Not available