Vulnerability-Lookup

CVE-2026-64400 (GCVE-0-2026-64400)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:50 – Updated: 2026-07-27 05:00

Title

ksmbd: prevent path traversal bypass by restricting caseless retry

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.

Severity

8.6 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

Assigner

Linux

References

2 references

URL	Tags
https://git.kernel.org/stable/c/8c9a4f1327eb71efb…
https://git.kernel.org/stable/c/54bab9ba5a9f156ff…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 74d7970febf7e9005375aeda0df821d2edffc9f7 , < 8c9a4f1327eb71efbf14842e7b8a6d965077eb67 (git) Affected: 74d7970febf7e9005375aeda0df821d2edffc9f7 , < 54bab9ba5a9f156ffa9324fcbe5a356fd0242f95 (git) Affected: 019aae488dbc67c97a33db03652e20e2c9e3afa7 (git) Affected: 6927ffe7479c72e7ebf885507227266a75f7c97d (git) Affected: ef6cc1c465786b3e4e735d1ab8b616b3e94402df (git) Affected: 5.15.145 , < 5.16 (semver) Affected: 6.1.71 , < 6.2 (semver) Affected: 6.3.10 , < 6.4 (semver)
Linux	Linux	Affected: 6.4 Unaffected: 0 , < 6.4 (semver) Unaffected: 7.1.4 , ≤ 7.1.* (semver) Unaffected: 7.2-rc1 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "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": "8c9a4f1327eb71efbf14842e7b8a6d965077eb67",
              "status": "affected",
              "version": "74d7970febf7e9005375aeda0df821d2edffc9f7",
              "versionType": "git"
            },
            {
              "lessThan": "54bab9ba5a9f156ffa9324fcbe5a356fd0242f95",
              "status": "affected",
              "version": "74d7970febf7e9005375aeda0df821d2edffc9f7",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "019aae488dbc67c97a33db03652e20e2c9e3afa7",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "6927ffe7479c72e7ebf885507227266a75f7c97d",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ef6cc1c465786b3e4e735d1ab8b616b3e94402df",
              "versionType": "git"
            },
            {
              "lessThan": "5.16",
              "status": "affected",
              "version": "5.15.145",
              "versionType": "semver"
            },
            {
              "lessThan": "6.2",
              "status": "affected",
              "version": "6.1.71",
              "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": "7.1.*",
              "status": "unaffected",
              "version": "7.1.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.4",
                  "versionStartIncluding": "6.4",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2-rc1",
                  "versionStartIncluding": "6.4",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "5.15.145",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "6.1.71",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "6.3.10",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.6,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H",
            "version": "3.1"
          }
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-27T05:00:31.935Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/8c9a4f1327eb71efbf14842e7b8a6d965077eb67"
        },
        {
          "url": "https://git.kernel.org/stable/c/54bab9ba5a9f156ffa9324fcbe5a356fd0242f95"
        }
      ],
      "title": "ksmbd: prevent path traversal bypass by restricting caseless retry",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64400",
    "datePublished": "2026-07-25T08:50:43.655Z",
    "dateReserved": "2026-07-19T15:36:31.785Z",
    "dateUpdated": "2026-07-27T05:00:31.935Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-64400",
      "date": "2026-07-26",
      "epss": "0.002",
      "percentile": "0.10176"
    },
    "microsoft_vex": {
      "current_release_date": "2026-07-26T01:06:38.000Z",
      "cve": "CVE-2026-64400",
      "id": "msrc_CVE-2026-64400",
      "initial_release_date": "2026-07-26T01:06:38.000Z",
      "product_status:under_investigation": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "ksmbd: prevent path traversal bypass by restricting caseless retry",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-64400.json",
      "version": "1"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-64400\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-07-25T10:17:23.510\",\"lastModified\":\"2026-07-27T05:16:47.173\",\"vulnStatus\":\"Received\",\"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.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/smb/server/vfs.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"74d7970febf7e9005375aeda0df821d2edffc9f7\",\"lessThan\":\"8c9a4f1327eb71efbf14842e7b8a6d965077eb67\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"74d7970febf7e9005375aeda0df821d2edffc9f7\",\"lessThan\":\"54bab9ba5a9f156ffa9324fcbe5a356fd0242f95\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"019aae488dbc67c97a33db03652e20e2c9e3afa7\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6927ffe7479c72e7ebf885507227266a75f7c97d\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ef6cc1c465786b3e4e735d1ab8b616b3e94402df\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"5.15.145\",\"lessThan\":\"5.16\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"6.1.71\",\"lessThan\":\"6.2\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"6.3.10\",\"lessThan\":\"6.4\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/smb/server/vfs.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.4\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.4\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.4\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2-rc1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H\",\"baseScore\":8.6,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"LOW\",\"integrityImpact\":\"LOW\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":4.7}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/54bab9ba5a9f156ffa9324fcbe5a356fd0242f95\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8c9a4f1327eb71efbf14842e7b8a6d965077eb67\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "suse_vex": {
      "aggregate_severity": "not set",
      "current_release_date": "2026-07-25T16:00:03Z",
      "cve": "CVE-2026-64400",
      "id": "CVE-2026-64400",
      "initial_release_date": "2026-07-25T16:00:03Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-64400",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64400.json",
      "version": "2"
    }
  }
}

GHSA-CG5C-7728-29V7

Vulnerability from github – Published: 2026-07-25 12:31 – Updated: 2026-07-27 06:30

Details

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.

Severity

8.6 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-64400"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-25T10:17:23Z",
    "severity": "HIGH"
  },
  "details": "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": "GHSA-cg5c-7728-29v7",
  "modified": "2026-07-27T06:30:36Z",
  "published": "2026-07-25T12:31:34Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64400"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/54bab9ba5a9f156ffa9324fcbe5a356fd0242f95"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8c9a4f1327eb71efbf14842e7b8a6d965077eb67"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H",
      "type": "CVSS_V3"
    }
  ]
}

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

CVE-2026-64400 (GCVE-0-2026-64400)

GHSA-CG5C-7728-29V7

Tags

Sightings

Nomenclature