CVE-2026-64393 (GCVE-0-2026-64393)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:50 – Updated: 2026-08-05 12:41
VLAI
Title
ksmbd: run set info with opener credentials
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: run set info with opener credentials SMB2 SET_INFO handlers call path-based VFS helpers after checking the access mask granted to the SMB handle. Those helpers perform their owner, inode permission and LSM checks using the current ksmbd worker credentials. Run the complete SET_INFO dispatch with the credentials captured when the handle was opened. This also removes the separate security information credential setup and keeps all SET_INFO classes under one credential scope. Direct override_creds() is used because it can nest with the request credential overrides already used by rename and link helpers.
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: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 5cbabf3a71575cd31bc7785d92d4ab42338a654b (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < b35afd5cf8fab236ef21117e42ee45691d4ffa7b (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 0ce682867fd506f61f40c76bde7e4205bde34e87 (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 20ee516a62989a8d505ee432f9e59525ea23984e (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 8cc9ec711f5255167247a9ab6a7179b787426ed7 (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < b383bcad3d2fe634b26efbce53e22bbb5753a520 (git)
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Linux Linux Affected: 5.15
Unaffected: 0 , < 5.15 (semver)
Unaffected: 6.1.178 , ≤ 6.1.* (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)
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{
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              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.18.39",
              "versionType": "semver"
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            {
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              "status": "unaffected",
              "version": "7.1.4",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc1",
              "versionType": "original_commit_for_fix"
            }
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        }
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      "cpeApplicability": [
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          "nodes": [
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        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: run set info with opener credentials\n\nSMB2 SET_INFO handlers call path-based VFS helpers after checking the\naccess mask granted to the SMB handle. Those helpers perform their owner,\ninode permission and LSM checks using the current ksmbd worker credentials.\n\nRun the complete SET_INFO dispatch with the credentials captured when the\nhandle was opened. This also removes the separate security information\ncredential setup and keeps all SET_INFO classes under one credential scope.\n\nDirect override_creds() is used because it can nest with the request\ncredential overrides already used by rename and link helpers."
        }
      ],
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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": [
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              "lang": "en",
              "value": "AV:N - The vulnerable SMB2 SET_INFO handler is remotely reachable through ksmbd over TCP/445 or SMB Direct.\nAC:L - An attacker can deterministically open a handle and send a crafted SET_INFO request; no race or condition outside the attacker\u2019s control is required.\nPR:N - Although a valid SMB session, writable tree, and suitable handle are required, ksmbd supports passwordless guest sessions on writable shares, making exploitation possible without attacker privileges in a reasonable deployment.\nUI:N - The attacker directly opens the handle and submits the SET_INFO request without any victim action.\nS:U - The bypass affects files and services governed by the same host kernel and filesystem security authority, without crossing a virtualization or sandbox boundary.\nC:N - The flaw provides unauthorized mutation through metadata, xattr, and truncation operations but does not itself disclose file contents or kernel memory.\nI:H - Privileged worker credentials can bypass opener UID, group, capability, inode, and LSM checks, permitting protected metadata changes and destructive truncation of an affected file.\nA:H - Repeated SET_INFO requests can truncate critical files or corrupt security-relevant metadata and xattrs, potentially disabling dependent services or exhausting filesystem resources."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:41:30.510Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64393",
    "datePublished": "2026-07-25T08:50:39.239Z",
    "dateReserved": "2026-07-19T15:36:31.785Z",
    "dateUpdated": "2026-08-05T12:41:30.510Z",
    "state": "PUBLISHED"
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      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "ksmbd: run set info with opener credentials",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-64393.json",
      "version": "2"
    },
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    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-07-27T06:37:12+00:00",
      "cve": "CVE-2026-64393",
      "id": "CVE-2026-64393",
      "initial_release_date": "2026-07-25T00:00:00+00:00",
      "product_status:known_not_affected": "275",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ksmbd: run set info with opener credentials",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64393.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

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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.