FKIE_CVE-2026-64400

Vulnerability from fkie_nvd - Published: 2026-07-25 10:17 - Updated: 2026-10-30 13:19
Severity
8.6 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: prevent path traversal bypass by restricting caseless retry ksmbd_vfs_path_lookup() enforces LOOKUP_BENEATH to restrict path resolution within the share root. When a crafted path attempts to escape the share boundary using parent-directory components ('..'), vfs_path_parent_lookup() detects this and immediately fails, returning -EXDEV. However, a bug exists in __ksmbd_vfs_kern_path() under caseless mode. The function fails to intercept the -EXDEV error and erroneously falls through to the caseless retry logic, which is intended only for genuinely missing files. During this retry process, the path is reconstructed, leading to an unintended LOOKUP_BENEATH bypass that allows write-capable users to create zero-length files or directories outside the exported share. Fix this by ensuring that the execution only proceeds to the caseless lookup retry when the error is specifically -ENOENT. Any other errors, such as -EXDEV from a path traversal attempt, must be returned immediately.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/21f050439db157f2afcc19885dec14549ca6ffc0
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/54bab9ba5a9f156ffa9324fcbe5a356fd0242f95Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8c9a4f1327eb71efbf14842e7b8a6d965077eb67Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a1c331d98313380c38f616c8b28b890ec8ef9c28
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/cfb5a56c218888f9d74165dff0c282cd0be97983
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/eec1dd2586c4016b7555a5d047db2b3756459fb2
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/vfs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "21f050439db157f2afcc19885dec14549ca6ffc0",
              "status": "affected",
              "version": "6927ffe7479c72e7ebf885507227266a75f7c97d",
              "versionType": "git"
            },
            {
              "lessThan": "eec1dd2586c4016b7555a5d047db2b3756459fb2",
              "status": "affected",
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            },
            {
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            },
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            },
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            },
            {
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              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ef6cc1c465786b3e4e735d1ab8b616b3e94402df",
              "versionType": "git"
            },
            {
              "lessThan": "6.1.191",
              "status": "affected",
              "version": "6.1.71",
              "versionType": "semver"
            },
            {
              "lessThan": "5.16",
              "status": "affected",
              "version": "5.15.145",
              "versionType": "semver"
            },
            {
              "lessThan": "6.4",
              "status": "affected",
              "version": "6.3.10",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/vfs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.4"
            },
            {
              "lessThan": "6.4",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.191",
              "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"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "B98C9201-BF17-4E2C-84FF-75EE2AA94DC5",
              "versionEndExcluding": "5.16",
              "versionStartIncluding": "5.15.145",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "163E72B5-0F5D-49E2-AAEA-F11E02D730AD",
              "versionEndExcluding": "6.2",
              "versionStartIncluding": "6.1.71",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "39D96392-5639-49DA-9355-4E876D0A8B6C",
              "versionEndExcluding": "7.1.4",
              "versionStartIncluding": "6.3.10",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: prevent path traversal bypass by restricting caseless retry\n\nksmbd_vfs_path_lookup() enforces LOOKUP_BENEATH to restrict path\nresolution within the share root. When a crafted path attempts to\nescape the share boundary using parent-directory components (\u0027..\u0027),\nvfs_path_parent_lookup() detects this and immediately fails,\nreturning -EXDEV.\n\nHowever, a bug exists in __ksmbd_vfs_kern_path() under caseless mode.\nThe function fails to intercept the -EXDEV error and erroneously\nfalls through to the caseless retry logic, which is intended only\nfor genuinely missing files. During this retry process, the path\nis reconstructed, leading to an unintended LOOKUP_BENEATH bypass\nthat allows write-capable users to create zero-length files or\ndirectories outside the exported share.\n\nFix this by ensuring that the execution only proceeds to the caseless\nlookup retry when the error is specifically -ENOENT. Any other errors,\nsuch as -EXDEV from a path traversal attempt, must be returned immediately."
    }
  ],
  "id": "CVE-2026-64400",
  "lastModified": "2026-10-30T13:19:36.180",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 8.6,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 4.7,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-07-25T10:17:23.510",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/21f050439db157f2afcc19885dec14549ca6ffc0"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/54bab9ba5a9f156ffa9324fcbe5a356fd0242f95"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/8c9a4f1327eb71efbf14842e7b8a6d965077eb67"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a1c331d98313380c38f616c8b28b890ec8ef9c28"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/cfb5a56c218888f9d74165dff0c282cd0be97983"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/eec1dd2586c4016b7555a5d047db2b3756459fb2"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}



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