CVE-2026-64388 (GCVE-0-2026-64388)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:50 – Updated: 2026-10-30 12:27
VLAI
Title
smb/client: fix chown/chgrp with SMB3 POSIX Extensions
Summary
In the Linux kernel, the following vulnerability has been resolved: smb/client: fix chown/chgrp with SMB3 POSIX Extensions Ownership (chown) and group (chgrp) modifications were being ignored when mounting with SMB3 POSIX Extensions unless CIFS_MOUNT_CIFS_ACL or CIFS_MOUNT_MODE_FROM_SID were also explicitly set. Fix this by checking for posix_extensions in cifs_setattr_nounix() when updating UID and GID, ensuring that id_mode_to_cifs_acl() is called to map and set the ownership/group information on the server.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 15:40 UTC
CWE
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6639 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: b326614ea2159ea5c835d320f261d05d080cd201 , < c0fe1118a1471d459f76c3e70ff2abbf784ce6bf (git)
Affected: b326614ea2159ea5c835d320f261d05d080cd201 , < 6825a45f6b8ef76b0ee32649ec3d6e39ca143a18 (git)
Affected: b326614ea2159ea5c835d320f261d05d080cd201 , < 27ead8c5418af6bfab711079fecb9414d78d4cae (git)
Affected: b326614ea2159ea5c835d320f261d05d080cd201 , < 3eaec47518e126e6dcd1a48521d740278073f0ec (git)
Affected: b326614ea2159ea5c835d320f261d05d080cd201 , < 550cfb8a81181331d4d0f76ab75ee58a0bf41e3e (git)
Affected: b326614ea2159ea5c835d320f261d05d080cd201 , < 760ef2c579c2609cf17fb1cd5392f64d42d43d33 (git)
guessed Create a notification for this product.
Linux Linux Affected: 4.18
Unaffected: 0 , < 4.18 (semver)
Unaffected: 6.1.191 , ≤ 6.1.* (semver)
Unaffected: 6.6.160 , ≤ 6.6.* (semver)
Unaffected: 6.12.114 , ≤ 6.12.* (semver)
Unaffected: 6.18.57 , ≤ 6.18.* (semver)
Unaffected: 7.1.4 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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                    "type": "CWE"
                  }
                ]
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-10-16T15:40:08.065Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "product": "Linux",
              "programFiles": [
                "fs/smb/client/inode.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "lessThan": "6825a45f6b8ef76b0ee32649ec3d6e39ca143a18",
                  "status": "affected",
                  "version": "b326614ea2159ea5c835d320f261d05d080cd201",
                  "versionType": "git"
                },
                {
                  "lessThan": "27ead8c5418af6bfab711079fecb9414d78d4cae",
                  "status": "affected",
                  "version": "b326614ea2159ea5c835d320f261d05d080cd201",
                  "versionType": "git"
                },
                {
                  "lessThan": "3eaec47518e126e6dcd1a48521d740278073f0ec",
                  "status": "affected",
                  "version": "b326614ea2159ea5c835d320f261d05d080cd201",
                  "versionType": "git"
                },
                {
                  "lessThan": "550cfb8a81181331d4d0f76ab75ee58a0bf41e3e",
                  "status": "affected",
                  "version": "b326614ea2159ea5c835d320f261d05d080cd201",
                  "versionType": "git"
                },
                {
                  "lessThan": "760ef2c579c2609cf17fb1cd5392f64d42d43d33",
                  "status": "affected",
                  "version": "b326614ea2159ea5c835d320f261d05d080cd201",
                  "versionType": "git"
                }
              ]
            },
            {
              "defaultStatus": "affected",
              "product": "Linux",
              "programFiles": [
                "fs/smb/client/inode.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "status": "affected",
                  "version": "4.18"
                },
                {
                  "lessThan": "4.18",
                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.6.*",
                  "status": "unaffected",
                  "version": "6.6.160",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.12.*",
                  "status": "unaffected",
                  "version": "6.12.114",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.18.*",
                  "status": "unaffected",
                  "version": "6.18.57",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "7.1.*",
                  "status": "unaffected",
                  "version": "7.1.4",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "7.2",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.6.160",
                      "versionStartIncluding": "4.18",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.12.114",
                      "versionStartIncluding": "4.18",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.18.57",
                      "versionStartIncluding": "4.18",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "7.1.4",
                      "versionStartIncluding": "4.18",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "7.2",
                      "versionStartIncluding": "4.18",
                      "vulnerable": true
                    }
                  ],
                  "negate": false,
                  "operator": "OR"
                }
              ]
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb/client: fix chown/chgrp with SMB3 POSIX Extensions\n\nOwnership (chown) and group (chgrp) modifications were being ignored when\nmounting with SMB3 POSIX Extensions unless CIFS_MOUNT_CIFS_ACL or\nCIFS_MOUNT_MODE_FROM_SID were also explicitly set.\n\nFix this by checking for posix_extensions in cifs_setattr_nounix() when\nupdating UID and GID, ensuring that id_mode_to_cifs_acl() is called to map\nand set the ownership/group information on the server."
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "scenarios": [
                {
                  "lang": "en",
                  "value": "AV:L - The vulnerable branch is reached through local chown/chgrp syscalls on an already mounted SMB3 POSIX share; unsolicited SMB traffic cannot invoke it.\nAC:L - With the affected mount configuration, the client deterministically skips the ownership update and returns success; no race, heap layout, or uncontrollable timing is required.\nPR:L - A basic local user can exercise the path on accessible share objects, and noperm deliberately defers authorization to the server whose ownership check is bypassed because no request is sent. The attacker need not create the mount.\nUI:N - The attacker can invoke the syscall directly and exploit continued rights or falsely cached ownership through automated services without human action.\nS:U - The defect affects resources governed through the vulnerable kernel and mounted share without escaping a VM, sandbox, or other distinct security authority.\nC:H - Because the intended ownership change never reaches the server, the prior owner or group can retain read access to an entire data tree believed to have been transferred or revoked.\nI:H - The prior owner can retain arbitrary modification rights, while falsely cached privileged ownership can cause privileged consumers to trust or execute attacker-controlled content.\nA:H - Retained ownership of writable files or directories can permit truncation or deletion of an entire service data tree, and privileged execution through false ownership can cause a complete outage."
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-10-21T12:43:18.915Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "references": [
            {
              "url": "https://git.kernel.org/stable/c/6825a45f6b8ef76b0ee32649ec3d6e39ca143a18"
            },
            {
              "url": "https://git.kernel.org/stable/c/27ead8c5418af6bfab711079fecb9414d78d4cae"
            },
            {
              "url": "https://git.kernel.org/stable/c/3eaec47518e126e6dcd1a48521d740278073f0ec"
            },
            {
              "url": "https://git.kernel.org/stable/c/550cfb8a81181331d4d0f76ab75ee58a0bf41e3e"
            },
            {
              "url": "https://git.kernel.org/stable/c/760ef2c579c2609cf17fb1cd5392f64d42d43d33"
            }
          ],
          "title": "smb/client: fix chown/chgrp with SMB3 POSIX Extensions",
          "x_generator": {
            "engine": "bippy-1.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2026-64388",
        "datePublished": "2026-07-25T08:50:36.202Z",
        "dateReserved": "2026-07-19T15:36:31.784Z",
        "dateUpdated": "2026-10-21T12:43:18.915Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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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

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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON
How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

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    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.