GHSA-WRJV-H4C7-CJ2F
Vulnerability from github – Published: 2026-08-05 09:31 – Updated: 2026-08-19 18:32In 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.
{
"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": "HIGH"
},
"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": "2026-08-19T18:32:04Z",
"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/1b6740525f5af90868d557c31b496ae689c8c549"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2c307126ed8e7adddab82b8e31d962d3a2156ab1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/415d0fff0451ad7ad4caa910f2bb0f562f0fd60f"
},
{
"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": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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