{
  "cveId": "CVE-2026-53383",
  "url": "https://patchblox.com/security/cve/CVE-2026-53383",
  "summary": "CVE-2026-53383 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-53383, released July 20, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "linux: In the Linux kernel, the following vulnerability has been resolved:  ksmbd: reject non-VALID session in compound requ...",
  "description": "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-\u003Esess (the session bound by the first operation) and validates only the SessionId, then returns \u0022valid\u0022. It never re-checks work-\u003Esess-\u003Estate == 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-\u003Euser is still NULL (-\u003Euser 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-\u003Euser) with sess-\u003Euser == NULL (transport_ipc.c:687/701/704) -\u003E 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.",
  "published": "2026-07-19T12:16:49Z",
  "severity": "high",
  "cvss": 7.5,
  "cvssVector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
  "epss": 0.00664,
  "epssPercentile": 0.51971,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 12.15 (bookworm)",
      "fixedVersion": "6.1.177-1",
      "fix": "DEBIAN-CVE-2026-53383",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-53383",
      "released": "2026-07-20T12:58:36Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "6.12.95-1",
      "fix": "DEBIAN-CVE-2026-53383",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-53383",
      "released": "2026-07-20T12:58:36Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.0.14-1",
      "fix": "DEBIAN-CVE-2026-53383",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-53383",
      "released": "2026-07-20T12:58:36Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T06:59:42Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}