CVE-2026-64578 (GCVE-0-2026-64578)

Vulnerability from cvelistv5 – Published: 2026-08-05 08:09 – Updated: 2026-08-05 08:09
VLAI
Title
ksmbd: validate compound request size before reading StructureSize2
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.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 2c307126ed8e7adddab82b8e31d962d3a2156ab1 (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < f7550a91ab211726f59cb137523b7a9eae1ac6eb (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < f0e337e7db67cc1c832958bbb6c4026bdceacfdb (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < ea128f06d2fb2186f0cac0c9f3e953e4d1f5c29a (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 15b38176fd1530372905c602fde51fe89ec8c877 (git)
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Linux Linux Affected: 5.15
Unaffected: 0 , < 5.15 (semver)
Unaffected: 6.6.148 , ≤ 6.6.* (semver)
Unaffected: 6.12.101 , ≤ 6.12.* (semver)
Unaffected: 6.18.42 , ≤ 6.18.* (semver)
Unaffected: 7.1.6 , ≤ 7.1.* (semver)
Unaffected: 7.2-rc4 , ≤ * (original_commit_for_fix)
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{
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          "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."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T08:09:33.740Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/2c307126ed8e7adddab82b8e31d962d3a2156ab1"
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          "url": "https://git.kernel.org/stable/c/15b38176fd1530372905c602fde51fe89ec8c877"
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    "cveId": "CVE-2026-64578",
    "datePublished": "2026-08-05T08:09:33.740Z",
    "dateReserved": "2026-07-19T15:36:31.798Z",
    "dateUpdated": "2026-08-05T08:09:33.740Z",
    "state": "PUBLISHED"
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    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-08-06T10:39:14+00:00",
      "cve": "CVE-2026-64578",
      "id": "CVE-2026-64578",
      "initial_release_date": "2026-08-05T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ksmbd: validate compound request size before reading StructureSize2",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64578.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-08-06T01:06:17Z",
      "cve": "CVE-2026-64578",
      "id": "CVE-2026-64578",
      "initial_release_date": "2026-08-06T01:06:17Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-64578",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64578.json",
      "version": "2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.