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Review reviewCritical

CVE-2026-64391

Linux

In the Linux kernel, the following vulnerability has been resolved: ksmbd: use opener credentials for ADS I/O Alternate data streams are stored as xattrs. Unlike regular file I/O, their read and write paths therefore call VFS xattr helpers which recheck inode permissions and LSM policy using the current task credentials. Run ADS I/O with the credentials captured when the SMB handle was opened.

CVSS
9.8
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 9.8

Vulnerability overview

In the Linux kernel, the following vulnerability has been resolved: ksmbd: use opener credentials for ADS I/O Alternate data streams are stored as xattrs. Unlike regular file I/O, their read and write paths therefore call VFS xattr helpers which recheck inode permissions and LSM policy using the current task credentials. Run ADS I/O with the credentials captured when the SMB handle was opened.

Affected product and versions

Product
Linux
Affected versions
>= f44158485826c076335d6860d35872271a83791d < a8f5d39971bbad9340d49cd41b0e2da9452a649d, >= f44158485826c076335d6860d35872271a83791d < 2b4592cea214683de0f2ce6f8c22c097fb0ea1ab, >= f44158485826c076335d6860d35872271a83791d < 52a56cf53ec834c44ac1b4d16d585f26613ee5ce, >= f44158485826c076335d6860d35872271a83791d < baa5e094886fffa7e6272edcb5e08be5ce28262c, >= 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:N/UI:N/S:U/C:H/I:H/A:H
CWE
Not available