FKIE_CVE-2026-64578

Vulnerability from fkie_nvd - Published: 2026-08-05 08:16 - Updated: 2026-08-08 15:16
Severity
8.2 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Summary
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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/15b38176fd1530372905c602fde51fe89ec8c877
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/2c307126ed8e7adddab82b8e31d962d3a2156ab1
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ea128f06d2fb2186f0cac0c9f3e953e4d1f5c29a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f0e337e7db67cc1c832958bbb6c4026bdceacfdb
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f7550a91ab211726f59cb137523b7a9eae1ac6eb
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/smb2misc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "2c307126ed8e7adddab82b8e31d962d3a2156ab1",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            },
            {
              "lessThan": "f7550a91ab211726f59cb137523b7a9eae1ac6eb",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            },
            {
              "lessThan": "f0e337e7db67cc1c832958bbb6c4026bdceacfdb",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            },
            {
              "lessThan": "ea128f06d2fb2186f0cac0c9f3e953e4d1f5c29a",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            },
            {
              "lessThan": "15b38176fd1530372905c602fde51fe89ec8c877",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/smb2misc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.15"
            },
            {
              "lessThan": "5.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.148",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.101",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.42",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc4",
              "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: 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": "CVE-2026-64578",
  "lastModified": "2026-08-08T15:16:32.803",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 8.2,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "LOW",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 4.2,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-05T08:16:37.760",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/15b38176fd1530372905c602fde51fe89ec8c877"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/2c307126ed8e7adddab82b8e31d962d3a2156ab1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ea128f06d2fb2186f0cac0c9f3e953e4d1f5c29a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f0e337e7db67cc1c832958bbb6c4026bdceacfdb"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f7550a91ab211726f59cb137523b7a9eae1ac6eb"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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