GHSA-WRJV-H4C7-CJ2F

Vulnerability from github – Published: 2026-08-05 09:31 – Updated: 2026-08-05 09:31
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: validate compound request size before reading StructureSize2

When ksmbd validates a compound (chained) SMB2 request, ksmbd_smb2_check_message() reads pdu->StructureSize2 without first checking that the compound element is large enough to contain it. StructureSize2 is a 2-byte field at offset 64 (__SMB2_HEADER_STRUCTURE_SIZE) from the start of each element.

The compound-walking logic only guarantees that a full 64-byte SMB2 header is present for the trailing element: when NextCommand is 0, len is reduced to the number of bytes remaining after next_smb2_rcv_hdr_off. A remote client can craft a compound request whose last element has exactly 64 bytes, so the 2-byte StructureSize2 read at offset 64 extends one byte past the receive buffer, producing a slab-out-of-bounds read.

BUG: KASAN: slab-out-of-bounds in ksmbd_smb2_check_message (fs/smb/server/smb2misc.c:402) Read of size 2 at addr ffff888012ae31ac by task kworker/0:1/14 The buggy address is located 172 bytes inside of allocated 173-byte region Workqueue: ksmbd-io handle_ksmbd_work Call Trace: ... kasan_report (mm/kasan/report.c:595) ksmbd_smb2_check_message (fs/smb/server/smb2misc.c:402) handle_ksmbd_work (fs/smb/server/server.c:119) process_one_work (kernel/workqueue.c:3314) worker_thread (kernel/workqueue.c:3397) kthread (kernel/kthread.c:436) ret_from_fork (arch/x86/kernel/process.c:158) ret_from_fork_asm (arch/x86/entry/entry_64.S:245)

Reject any compound element that is too small to hold StructureSize2 before dereferencing it.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-64578"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-05T08:16:37Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: validate compound request size before reading StructureSize2\n\nWhen ksmbd validates a compound (chained) SMB2 request,\nksmbd_smb2_check_message() reads pdu-\u003eStructureSize2 without first\nchecking that the compound element is large enough to contain it.\nStructureSize2 is a 2-byte field at offset 64\n(__SMB2_HEADER_STRUCTURE_SIZE) from the start of each element.\n\nThe compound-walking logic only guarantees that a full 64-byte SMB2\nheader is present for the trailing element: when NextCommand is 0, len is\nreduced to the number of bytes remaining after next_smb2_rcv_hdr_off. A\nremote client can craft a compound request whose last element has exactly\n64 bytes, so the 2-byte StructureSize2 read at offset 64 extends one byte\npast the receive buffer, producing a slab-out-of-bounds read.\n\n  BUG: KASAN: slab-out-of-bounds in ksmbd_smb2_check_message (fs/smb/server/smb2misc.c:402)\n  Read of size 2 at addr ffff888012ae31ac by task kworker/0:1/14\n  The buggy address is located 172 bytes inside of allocated 173-byte region\n  Workqueue: ksmbd-io handle_ksmbd_work\n  Call Trace:\n   ...\n   kasan_report (mm/kasan/report.c:595)\n   ksmbd_smb2_check_message (fs/smb/server/smb2misc.c:402)\n   handle_ksmbd_work (fs/smb/server/server.c:119)\n   process_one_work (kernel/workqueue.c:3314)\n   worker_thread (kernel/workqueue.c:3397)\n   kthread (kernel/kthread.c:436)\n   ret_from_fork (arch/x86/kernel/process.c:158)\n   ret_from_fork_asm (arch/x86/entry/entry_64.S:245)\n\nReject any compound element that is too small to hold StructureSize2\nbefore dereferencing it.",
  "id": "GHSA-wrjv-h4c7-cj2f",
  "modified": "2026-08-05T09:31:17Z",
  "published": "2026-08-05T09:31:17Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64578"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/15b38176fd1530372905c602fde51fe89ec8c877"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2c307126ed8e7adddab82b8e31d962d3a2156ab1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ea128f06d2fb2186f0cac0c9f3e953e4d1f5c29a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f0e337e7db67cc1c832958bbb6c4026bdceacfdb"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f7550a91ab211726f59cb137523b7a9eae1ac6eb"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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