Answer in brief
CVE-2026-53383 records a Unknown severity vulnerability in ksmbd: reject non-VALID session in compound request branch. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
Answer in brief
CVE-2026-53383 records a Unknown severity vulnerability in ksmbd: reject non-VALID session in compound request branch. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=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 | 25ff12b82a376ff5c4583102a63d2456a6b9ebb9, fc578523a72cb8b329d32070b95898e81613cc3f, d2bbbb6c55812220fee5d801c275cc267ea3cbeb, 8f0302fb691537d33ec8f668565257ea9d340ffe, 7cad3ceaf679c55bc9946685dacafce78ce6b51a, 06e1f05a1dbe8bbd054c0927b17fc0a61cc8bef7, 5f983b864d3d473ac533b2f4f44a1bbe5dcbccf4, 609ca17d869d04ba249e32cdcbf13c0b1c66f43c, 5.15.211, 6.1.177, 6.4 |
| Linux/Linuxgeneric | 6.4 | Not reported |
Published upstream
Jul 19, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
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_SETUP state machine) does enforce the VALID state; the compound branch bypasses all of it. A SESSION_SETUP carrying only an NTLM Type-1 (NtLmNegotiate) blob publishes a fresh SMB2_SESSION_IN_PROGRESS session whose sess->user is still NULL (->user is assigned later, by ntlm_authenticate()). Used as operation 1 of a COMPOUND with operation 2 = TREE_CONNECT (related, SessionId=ULLONG_MAX, \\host\IPC$), the tree-connect then runs on that IN_PROGRESS session and reaches ksmbd_ipc_tree_connect_request(), which dereferences user_name(sess->user) with sess->user == NULL (transport_ipc.c:687/701/704) -> remote NULL-pointer dereference and a kernel Oops that wedges the ksmbd worker for all clients. Reject any non-first compound operation that lands on a session which is not SMB2_SESSION_VALID, mirroring the validity the standalone lookup path enforces. SESSION_SETUP itself legitimately runs on an IN_PROGRESS session, but it is never carried as a non-first compound operation, so multi-leg authentication is unaffected by this check.
Quoted source text, attributed separately from HOL analysis.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=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 | 25ff12b82a376ff5c4583102a63d2456a6b9ebb9, fc578523a72cb8b329d32070b95898e81613cc3f, d2bbbb6c55812220fee5d801c275cc267ea3cbeb, 8f0302fb691537d33ec8f668565257ea9d340ffe, 7cad3ceaf679c55bc9946685dacafce78ce6b51a, 06e1f05a1dbe8bbd054c0927b17fc0a61cc8bef7, 5f983b864d3d473ac533b2f4f44a1bbe5dcbccf4, 609ca17d869d04ba249e32cdcbf13c0b1c66f43c, 5.15.211, 6.1.177, 6.4 |
| Linux/Linuxgeneric | 6.4 | Not reported |
Published upstream
Jul 19, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
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_SETUP state machine) does enforce the VALID state; the compound branch bypasses all of it. A SESSION_SETUP carrying only an NTLM Type-1 (NtLmNegotiate) blob publishes a fresh SMB2_SESSION_IN_PROGRESS session whose sess->user is still NULL (->user is assigned later, by ntlm_authenticate()). Used as operation 1 of a COMPOUND with operation 2 = TREE_CONNECT (related, SessionId=ULLONG_MAX, \\host\IPC$), the tree-connect then runs on that IN_PROGRESS session and reaches ksmbd_ipc_tree_connect_request(), which dereferences user_name(sess->user) with sess->user == NULL (transport_ipc.c:687/701/704) -> remote NULL-pointer dereference and a kernel Oops that wedges the ksmbd worker for all clients. Reject any non-first compound operation that lands on a session which is not SMB2_SESSION_VALID, mirroring the validity the standalone lookup path enforces. SESSION_SETUP itself legitimately runs on an IN_PROGRESS session, but it is never carried as a non-first compound operation, so multi-leg authentication is unaffected by this check.
Quoted source text, attributed separately from HOL analysis.