Vulnerability-Lookup

CVE-2025-40328 (GCVE-0-2025-40328)

Vulnerability from cvelistv5 – Published: 2025-12-09 04:09 – Updated: 2026-08-05 12:09

Title

smb: client: fix potential UAF in smb2_close_cached_fid()

Summary

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix potential UAF in smb2_close_cached_fid() find_or_create_cached_dir() could grab a new reference after kref_put() had seen the refcount drop to zero but before cfid_list_lock is acquired in smb2_close_cached_fid(), leading to use-after-free. Switch to kref_put_lock() so cfid_release() is called with cfid_list_lock held, closing that gap.

Severity

8.8 (High)


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

Assigner

Linux mitre root

References

4 references

URL	Tags
https://git.kernel.org/stable/c/cb52d9c86d70298de…
https://git.kernel.org/stable/c/065bd62412271a2d7…
https://git.kernel.org/stable/c/bdb596ceb4b7c3f28…
https://git.kernel.org/stable/c/734e99623c5b65bf2…

Impacted products

2 products

Vendor	Product	Version	CPE status
Linux	Linux	Affected: ebe98f1447bbccf8228335c62d86af02a0ed23f7 , < cb52d9c86d70298de0ab7c7953653898cbc0efd6 (git) Affected: ebe98f1447bbccf8228335c62d86af02a0ed23f7 , < 065bd62412271a2d734810dd50336cae88c54427 (git) Affected: ebe98f1447bbccf8228335c62d86af02a0ed23f7 , < bdb596ceb4b7c3f28786a33840263728217fbcf5 (git) Affected: ebe98f1447bbccf8228335c62d86af02a0ed23f7 , < 734e99623c5b65bf2c03e35978a0b980ebc3c2f8 (git)	guessed
Linux	Linux	Affected: 6.1 Unaffected: 0 , < 6.1 (semver) Unaffected: 6.6.117 , ≤ 6.6.* (semver) Unaffected: 6.12.58 , ≤ 6.12.* (semver) Unaffected: 6.17.8 , ≤ 6.17.* (semver) Unaffected: 6.18 , ≤ * (original_commit_for_fix)	guessed

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/client/cached_dir.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "cb52d9c86d70298de0ab7c7953653898cbc0efd6",
              "status": "affected",
              "version": "ebe98f1447bbccf8228335c62d86af02a0ed23f7",
              "versionType": "git"
            },
            {
              "lessThan": "065bd62412271a2d734810dd50336cae88c54427",
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              "version": "ebe98f1447bbccf8228335c62d86af02a0ed23f7",
              "versionType": "git"
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              "status": "affected",
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              "versionType": "git"
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              "status": "affected",
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              "versionType": "git"
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          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/client/cached_dir.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.1"
            },
            {
              "lessThan": "6.1",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.117",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.58",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.17.*",
              "status": "unaffected",
              "version": "6.17.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.18",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.117",
                  "versionStartIncluding": "6.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.58",
                  "versionStartIncluding": "6.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "6.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18",
                  "versionStartIncluding": "6.1",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix potential UAF in smb2_close_cached_fid()\n\nfind_or_create_cached_dir() could grab a new reference after kref_put()\nhad seen the refcount drop to zero but before cfid_list_lock is acquired\nin smb2_close_cached_fid(), leading to use-after-free.\n\nSwitch to kref_put_lock() so cfid_release() is called with\ncfid_list_lock held, closing that gap."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The freeing side of the race is driven directly by a remote peer \u2014 `smb2_is_valid_lease_break()` (fs/smb/client/smb2misc.c:692) processes unsolicited SMB2 lease-break packets from the server and calls `cached_dir_lease_break()`, which clears the lease ref and queues the final `kref_put()`; server-forced reconnects similarly drive `invalidate_all_cached_dirs()`. A malicious, compromised, or MITM\u0027d SMB server therefore triggers the vulnerable refcount transition over the network.\nAC:L - The attacker controls the timing and rate of lease breaks/reconnects and can replay them indefinitely against routine directory activity on the mount, so the narrow window between `refcount_dec_and_test()` and the lock acquisition can be hit reliably by repetition. Race conditions the attacker can retry at will are Low complexity.\nPR:N - A malicious or MITM SMB server needs no credentials or privileges on the victim host; lease-break notifications are unsolicited server-to-client messages processed by the demultiplex thread. In the local variant the trigger is plain rmdir/stat/readdir on an accessible mount, requiring at most an unprivileged account.\nUI:R - Exploitation requires the victim to have the attacker-controlled SMB share mounted and to be performing directory lookups on it so that `find_or_create_cached_dir()` runs concurrently with the release path. The server cannot force that local access itself.\nS:U - The use-after-free is on a kernel slab object (`struct cached_fid`) and the impact stays within the kernel\u0027s own security authority \u2014 no VM, IOMMU, or sandbox boundary is crossed.\nC:H - A freed `cached_fid` holding `dentry`, `tcon`, `cifs_fid` handles, a mutex and list/work heads can be reallocated and sprayed with attacker-chosen data; the racing thread then reads it and returns cached directory/file_all_info state, giving a path to disclosing kernel memory. Per guidance, use-after-free is scored High for confidentiality.\nI:H - The stale object is written through as well as read (`kref_get`, `last_access_time`, list manipulation, `dput(cfid-\u003edentry)` on a reused pointer, and `SMB2_close()` on stale fid values), so heap grooming turns this into a write primitive over reallocated slab contents and potential control-flow hijack via the embedded `work_struct` function pointers.\nA:H - Losing the race produces a `refcount_t: addition on 0` warning followed by dereference and double-free of the `cached_fid` \u2014 including `dput()` on a freed dentry and slab corruption \u2014 reliably causing an oops or kernel panic."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:09:39.443Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/cb52d9c86d70298de0ab7c7953653898cbc0efd6"
        },
        {
          "url": "https://git.kernel.org/stable/c/065bd62412271a2d734810dd50336cae88c54427"
        },
        {
          "url": "https://git.kernel.org/stable/c/bdb596ceb4b7c3f28786a33840263728217fbcf5"
        },
        {
          "url": "https://git.kernel.org/stable/c/734e99623c5b65bf2c03e35978a0b980ebc3c2f8"
        }
      ],
      "title": "smb: client: fix potential UAF in smb2_close_cached_fid()",
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        "engine": "bippy-1.2.0"
      }
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  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40328",
    "datePublished": "2025-12-09T04:09:44.876Z",
    "dateReserved": "2025-04-16T07:20:57.186Z",
    "dateUpdated": "2026-08-05T12:09:39.443Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2025-40328",
      "date": "2026-09-17",
      "epss": "0.00461",
      "percentile": "0.39051"
    },
    "microsoft_vex": {
      "current_release_date": "2025-12-16T14:40:28.000Z",
      "cve": "CVE-2025-40328",
      "id": "msrc_CVE-2025-40328",
      "initial_release_date": "2025-12-02T00:00:00.000Z",
      "product_status:fixed": "1",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "smb: client: fix potential UAF in smb2_close_cached_fid()",
      "url": "https://msrc.microsoft.com/csaf/vex/2025/msrc_cve-2025-40328.json",
      "version": "2"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-40328\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-12-09T16:17:42.903\",\"lastModified\":\"2026-07-30T06:24:29.547\",\"vulnStatus\":\"Deferred\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nsmb: client: fix potential UAF in smb2_close_cached_fid()\\n\\nfind_or_create_cached_dir() could grab a new reference after kref_put()\\nhad seen the refcount drop to zero but before cfid_list_lock is acquired\\nin smb2_close_cached_fid(), leading to use-after-free.\\n\\nSwitch to kref_put_lock() so cfid_release() is called with\\ncfid_list_lock held, closing that gap.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/smb/client/cached_dir.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"ebe98f1447bbccf8228335c62d86af02a0ed23f7\",\"lessThan\":\"cb52d9c86d70298de0ab7c7953653898cbc0efd6\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ebe98f1447bbccf8228335c62d86af02a0ed23f7\",\"lessThan\":\"065bd62412271a2d734810dd50336cae88c54427\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ebe98f1447bbccf8228335c62d86af02a0ed23f7\",\"lessThan\":\"bdb596ceb4b7c3f28786a33840263728217fbcf5\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ebe98f1447bbccf8228335c62d86af02a0ed23f7\",\"lessThan\":\"734e99623c5b65bf2c03e35978a0b980ebc3c2f8\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/smb/client/cached_dir.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.1\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.1\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.117\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.58\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.17.8\",\"lessThanOrEqual\":\"6.17.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18\",\"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:R/S:U/C:H/I:H/A:H\",\"baseScore\":8.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"REQUIRED\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":2.8,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/065bd62412271a2d734810dd50336cae88c54427\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/734e99623c5b65bf2c03e35978a0b980ebc3c2f8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/bdb596ceb4b7c3f28786a33840263728217fbcf5\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/cb52d9c86d70298de0ab7c7953653898cbc0efd6\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-21T20:04:51+00:00",
      "cve": "CVE-2025-40328",
      "id": "CVE-2025-40328",
      "initial_release_date": "2025-12-09T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: smb: client: fix potential UAF in smb2_close_cached_fid()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-40328.json",
      "version": "3"
    }
  }
}

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.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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CVE-2025-40328 (GCVE-0-2025-40328)

Tags

Sightings

Nomenclature

Related by attack behaviour