FKIE_CVE-2026-53383

Vulnerability from fkie_nvd - Published: 2026-07-19 12:16 - Updated: 2026-07-20 15:16
Severity
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Summary
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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/06e1f05a1dbe8bbd054c0927b17fc0a61cc8bef7
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/25ff12b82a376ff5c4583102a63d2456a6b9ebb9
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5f983b864d3d473ac533b2f4f44a1bbe5dcbccf4
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/609ca17d869d04ba249e32cdcbf13c0b1c66f43c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7cad3ceaf679c55bc9946685dacafce78ce6b51a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8f0302fb691537d33ec8f668565257ea9d340ffe
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d2bbbb6c55812220fee5d801c275cc267ea3cbeb
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/fc578523a72cb8b329d32070b95898e81613cc3f
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/smb2pdu.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "25ff12b82a376ff5c4583102a63d2456a6b9ebb9",
              "status": "affected",
              "version": "eb947403518ea3d93f6d89264bb1f5416bb0c7d0",
              "versionType": "git"
            },
            {
              "lessThan": "fc578523a72cb8b329d32070b95898e81613cc3f",
              "status": "affected",
              "version": "854156d12caa9d36de1cf5f084591c7686cc8a9d",
              "versionType": "git"
            },
            {
              "lessThan": "d2bbbb6c55812220fee5d801c275cc267ea3cbeb",
              "status": "affected",
              "version": "5005bcb4219156f1bf7587b185080ec1da08518e",
              "versionType": "git"
            },
            {
              "lessThan": "8f0302fb691537d33ec8f668565257ea9d340ffe",
              "status": "affected",
              "version": "5005bcb4219156f1bf7587b185080ec1da08518e",
              "versionType": "git"
            },
            {
              "lessThan": "7cad3ceaf679c55bc9946685dacafce78ce6b51a",
              "status": "affected",
              "version": "5005bcb4219156f1bf7587b185080ec1da08518e",
              "versionType": "git"
            },
            {
              "lessThan": "06e1f05a1dbe8bbd054c0927b17fc0a61cc8bef7",
              "status": "affected",
              "version": "5005bcb4219156f1bf7587b185080ec1da08518e",
              "versionType": "git"
            },
            {
              "lessThan": "5f983b864d3d473ac533b2f4f44a1bbe5dcbccf4",
              "status": "affected",
              "version": "5005bcb4219156f1bf7587b185080ec1da08518e",
              "versionType": "git"
            },
            {
              "lessThan": "609ca17d869d04ba249e32cdcbf13c0b1c66f43c",
              "status": "affected",
              "version": "5005bcb4219156f1bf7587b185080ec1da08518e",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "d1066c1b3663401cd23c0d6e60cdae750ce00c0f",
              "versionType": "git"
            },
            {
              "lessThan": "5.15.211",
              "status": "affected",
              "version": "5.15.121",
              "versionType": "semver"
            },
            {
              "lessThan": "6.1.177",
              "status": "affected",
              "version": "6.1.36",
              "versionType": "semver"
            },
            {
              "lessThan": "6.4",
              "status": "affected",
              "version": "6.3.10",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/smb2pdu.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.4"
            },
            {
              "lessThan": "6.4",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.211",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.177",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.144",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.95",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.37",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.14",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.2",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: reject non-VALID session in compound request branch\n\nsmb2_check_user_session() takes a shortcut for any operation that is not\nthe first in a COMPOUND request: it reuses work-\u003esess (the session bound by\nthe first operation) and validates only the SessionId, then returns\n\"valid\". It never re-checks work-\u003esess-\u003estate == SMB2_SESSION_VALID, and a\nSessionId of 0xFFFFFFFFFFFFFFFF (ULLONG_MAX, the MS-SMB2 related-operation\nvalue) skips even the id comparison. The standalone path\n(ksmbd_session_lookup_all() plus the SESSION_SETUP state machine) does\nenforce the VALID state; the compound branch bypasses all of it.\n\nA SESSION_SETUP carrying only an NTLM Type-1 (NtLmNegotiate) blob publishes\na fresh SMB2_SESSION_IN_PROGRESS session whose sess-\u003euser is still NULL\n(-\u003euser is assigned later, by ntlm_authenticate()). Used as operation 1 of\na COMPOUND with operation 2 = TREE_CONNECT (related, SessionId=ULLONG_MAX,\n\\\\host\\IPC$), the tree-connect then runs on that IN_PROGRESS session and\nreaches ksmbd_ipc_tree_connect_request(), which dereferences\nuser_name(sess-\u003euser) with sess-\u003euser == NULL (transport_ipc.c:687/701/704)\n-\u003e remote NULL-pointer dereference and a kernel Oops that wedges the ksmbd\nworker for all clients.\n\nReject any non-first compound operation that lands on a session which is\nnot SMB2_SESSION_VALID, mirroring the validity the standalone lookup path\nenforces. SESSION_SETUP itself legitimately runs on an IN_PROGRESS session,\nbut it is never carried as a non-first compound operation, so multi-leg\nauthentication is unaffected by this check."
    }
  ],
  "id": "CVE-2026-53383",
  "lastModified": "2026-07-20T15:16:40.797",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-07-19T12:16:49.117",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/06e1f05a1dbe8bbd054c0927b17fc0a61cc8bef7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/25ff12b82a376ff5c4583102a63d2456a6b9ebb9"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/5f983b864d3d473ac533b2f4f44a1bbe5dcbccf4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/609ca17d869d04ba249e32cdcbf13c0b1c66f43c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7cad3ceaf679c55bc9946685dacafce78ce6b51a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8f0302fb691537d33ec8f668565257ea9d340ffe"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d2bbbb6c55812220fee5d801c275cc267ea3cbeb"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/fc578523a72cb8b329d32070b95898e81613cc3f"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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