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Review reviewHigh

CVE-2026-53383

Linux Linux, linux kernel

In the Linux kernel, the following vulnerability has been resolved: ksmbd: reject non-VALID session in compound request branch smb2_check_user_session() takes a shortcut for any operation that is not the first in a COMPOUND request: it reuses work->sess (the session bound by the first operation) and validates only the SessionId, then returns "valid". It never re-checks work->sess->state == SMB2_SESSION_VALID, and a SessionId of 0xFFFFFFFFFFFFFFFF (ULLONG_MAX, the MS-SMB2 related-operation value) skips even the id comparison. The standalone path (ksmbd_session_lookup_all() plus the SESSION_S...

CVSS
7.5
EPSS
0.69%
49.1% percentile
CISA KEV
Not listed
Published
2026.07.19
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.69%
Technical severityCVSS 7.5

Vulnerability overview

In the Linux kernel, the following vulnerability has been resolved: ksmbd: reject non-VALID session in compound request branch smb2_check_user_session() takes a shortcut for any operation that is not the first in a COMPOUND request: it reuses work->sess (the session bound by the first operation) and validates only the SessionId, then returns "valid". It never re-checks work->sess->state == SMB2_SESSION_VALID, and a SessionId of 0xFFFFFFFFFFFFFFFF (ULLONG_MAX, the MS-SMB2 related-operation value) skips even the id comparison. The standalone path (ksmbd_session_lookup_all() plus the SESSION_S...

Affected product and versions

Product
Linux Linux, linux kernel
Affected versions
>= eb947403518ea3d93f6d89264bb1f5416bb0c7d0 < 25ff12b82a376ff5c4583102a63d2456a6b9ebb9, >= 854156d12caa9d36de1cf5f084591c7686cc8a9d < fc578523a72cb8b329d32070b95898e81613cc3f, >= 5005bcb4219156f1bf7587b185080ec1da08518e < d2bbbb6c55812220fee5d801c275cc267ea3cbeb, >= 5005bcb4219156f1bf7587b185080ec1da08518e < 8f0302fb691537d33ec8f668565257ea9d340ffe, >= 5005bcb4219156f1bf7587b185080ec1da08518e < 7cad3ceaf679c55bc9946685dacafce78ce6b51a, >= 5005bcb4219156f1bf7587b185080ec1da08518e < 06e1f05a1dbe8bbd054c0927b17fc0a61cc8bef7, >= 5005bcb4219156f1bf7587b185080ec1da08518e < 5f983b864d3d473ac533b2f4f44a1bbe5dcbccf4, >= 5005bcb4219156f1bf7587b185080ec1da08518e < 609ca17d869d04ba249e32cdcbf13c0b1c66f43c, >= d1066c1b3663401cd23c0d6e60cdae750ce00c0f, >= 5.15.121 < 5.15.211, >= 6.1.36 < 6.1.177, >= 6.3.10 < 6.4, >= 6.4, >= 6.4.1 < 6.6.144, >= 6.7 < 6.12.95, >= 6.13 < 6.18.37, >= 6.19 < 7.0.14, >= 7.1 < 7.1.2, 6.4
Fixed versions
5.15.211, 6.1.177, 6.4, 6.6.144, 6.12.95, 6.18.37, 7.0.14, 7.1.2

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Linux Linux, linux kernel 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:N/I:N/A:H
CWE
CWE-476