CVE-2026-64392 (GCVE-0-2026-64392)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:50 – Updated: 2026-08-05 12:41
VLAI
Title
ksmbd: use opener credentials for delete-on-close
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: use opener credentials for delete-on-close Delete-on-close can be completed by deferred or durable handle teardown, where no request work is available. Both the base-file unlink and the ADS xattr removal consequently run with the ksmbd worker credentials and can bypass filesystem permission checks. Run both operations with the credentials captured in struct file when the handle was opened. This preserves the authenticated user's fsuid, fsgid, supplementary groups and capability restrictions at final close.
Severity
9.1 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: f44158485826c076335d6860d35872271a83791d , < f08b3f451f12eee4abd8a5981803bc36db84458b (git)
Affected: f44158485826c076335d6860d35872271a83791d , < 18c59109bb6fb816d5102171666f87cf1e29901d (git)
Affected: f44158485826c076335d6860d35872271a83791d , < e72c15085b6d86f45d224d98aa75b5cace4aaab9 (git)
Affected: f44158485826c076335d6860d35872271a83791d , < 4b7059974549d278e30fe70e2a4e421f9839817d (git)
Affected: f44158485826c076335d6860d35872271a83791d , < 52e2f21911158ec961cd5aae19c56460db382af0 (git)
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Linux Linux Affected: 5.15
Unaffected: 0 , < 5.15 (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.96 , ≤ 6.12.* (semver)
Unaffected: 6.18.39 , ≤ 6.18.* (semver)
Unaffected: 7.1.4 , ≤ 7.1.* (semver)
Unaffected: 7.2-rc1 , ≤ * (original_commit_for_fix)
Create a notification for this product.
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/vfs.c",
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          "vendor": "Linux",
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            }
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        }
      ],
      "cpeApplicability": [
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: use opener credentials for delete-on-close\n\nDelete-on-close can be completed by deferred or durable handle teardown,\nwhere no request work is available. Both the base-file unlink and the ADS\nxattr removal consequently run with the ksmbd worker credentials and can\nbypass filesystem permission checks.\n\nRun both operations with the credentials captured in struct file when the\nhandle was opened. This preserves the authenticated user\u0027s fsuid, fsgid,\nsupplementary groups and capability restrictions at final close."
        }
      ],
      "metrics": [
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            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - A remote SMB client reaches the vulnerable CREATE, SET_INFO, and CLOSE paths through ksmbd over TCP/445.\nAC:L - The attacker can deterministically request delete-on-close and close or disconnect the handle; no race or condition outside attacker control is required.\nPR:N - Although a valid SMB session and writable tree are required, ksmbd supports anonymous guest sessions, making exploitation possible without prior privileges on a reasonably configured writable guest share.\nUI:N - Exploitation requires only attacker-generated SMB requests and no action by another user.\nS:U - The unauthorized filesystem operations occur within the same host and kernel security authority, without crossing a VM, sandbox, or IOMMU boundary.\nC:N - The flaw only unlinks filesystem objects or removes ADS xattrs; it provides no read primitive, information disclosure, or memory corruption.\nI:H - The privileged worker can delete attacker-selected files, empty directories, or ADS data despite the opener\u0027s filesystem restrictions, permitting complete destruction or replacement of protected exported data.\nA:H - The attacker can repeatedly and recursively delete exported resources, potentially causing complete loss of critical share data or services that depend on it."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:41:29.430Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/f08b3f451f12eee4abd8a5981803bc36db84458b"
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        {
          "url": "https://git.kernel.org/stable/c/52e2f21911158ec961cd5aae19c56460db382af0"
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      ],
      "title": "ksmbd: use opener credentials for delete-on-close",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64392",
    "datePublished": "2026-07-25T08:50:38.634Z",
    "dateReserved": "2026-07-19T15:36:31.785Z",
    "dateUpdated": "2026-08-05T12:41:29.430Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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      "date": "2026-08-10",
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      "percentile": "0.38163"
    },
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      "cve": "CVE-2026-64392",
      "id": "msrc_CVE-2026-64392",
      "initial_release_date": "2026-07-26T01:09:38.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "ksmbd: use opener credentials for delete-on-close",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-64392.json",
      "version": "2"
    },
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    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-08-05T14:10:50+00:00",
      "cve": "CVE-2026-64392",
      "id": "CVE-2026-64392",
      "initial_release_date": "2026-07-25T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ksmbd: use opener credentials for delete-on-close",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64392.json",
      "version": "3"
    }
  }
}



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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

Author Source Type Date Other

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.