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GHSA-CFRM-7RJV-HJ84

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:

smb: client: reject overlapping data areas in SMB2 responses

Commit 53b7c271f06b ("smb: client: restrict implied bcc[0] exemption to responses without data area") restricted the implied bcc[0] length exception to responses without a data area. However, the overlap handling in __smb2_calc_size() clears data_length, which can make an invalid response appear to have no data area and so qualify for the exception.

Track data area overlap separately and reject such responses before applying the length compatibility exceptions.

Severity

9.1 (Critical)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-64257"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-25T10:17:05Z",
    "severity": "CRITICAL"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: reject overlapping data areas in SMB2 responses\n\nCommit 53b7c271f06b (\"smb: client: restrict implied bcc[0] exemption to\nresponses without data area\") restricted the implied bcc[0] length\nexception to responses without a data area. However, the overlap\nhandling in __smb2_calc_size() clears data_length, which can make an\ninvalid response appear to have no data area and so qualify for the\nexception.\n\nTrack data area overlap separately and reject such responses before\napplying the length compatibility exceptions.",
  "id": "GHSA-cfrm-7rjv-hj84",
  "modified": "2026-07-27T06:30:31Z",
  "published": "2026-07-25T12:31:27Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64257"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/36bfa52459e45c0d5b668de2f1c91f6dc5c67775"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/445ece263131780dee273d727a4d6f11934feec7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4a9d2657d3e05f6ed09c148cb127b4e58702275f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/57cba95f0e97c6f6e45e6731da30aff091bd7460"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8986c932905ea508d66da421eb2eb6e676ace1fe"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fdafa1e68dc75045b7b617e6e7d2854950804d83"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-64257 (GCVE-0-2026-64257)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:49 – Updated: 2026-08-17 04:52

Title

smb: client: reject overlapping data areas in SMB2 responses

Summary

In the Linux kernel, the following vulnerability has been resolved: smb: client: reject overlapping data areas in SMB2 responses Commit 53b7c271f06b ("smb: client: restrict implied bcc[0] exemption to responses without data area") restricted the implied bcc[0] length exception to responses without a data area. However, the overlap handling in __smb2_calc_size() clears data_length, which can make an invalid response appear to have no data area and so qualify for the exception. Track data area overlap separately and reject such responses before applying the length compatibility exceptions.

Severity

9.1 (Critical)


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

Assigner

Linux mitre root Scorecard

References

6 references

URL	Tags
https://git.kernel.org/stable/c/445ece263131780de…
https://git.kernel.org/stable/c/36bfa52459e45c0d5…
https://git.kernel.org/stable/c/4a9d2657d3e05f6ed…
https://git.kernel.org/stable/c/fdafa1e68dc75045b…
https://git.kernel.org/stable/c/57cba95f0e97c6f6e…
https://git.kernel.org/stable/c/8986c932905ea508d…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 31c6312608c60b72a1feb99a5afb680645a3e8a3 , < 445ece263131780dee273d727a4d6f11934feec7 (git) Affected: 573e502d14714d2947e22e7eff40ec20a6a44a42 , < 36bfa52459e45c0d5b668de2f1c91f6dc5c67775 (git) Affected: 419ec1b604d7fb60c10aec2dc062371f9fcd4940 , < 4a9d2657d3e05f6ed09c148cb127b4e58702275f (git) Affected: ceb875a375dedbf51c9425c1d13a2d7a8435c08c , < fdafa1e68dc75045b7b617e6e7d2854950804d83 (git) Affected: 6e9d10f62773b99bd927940fd9cbdfe7207e23ff , < 57cba95f0e97c6f6e45e6731da30aff091bd7460 (git) Affected: 53b7c271f06be4dd5cfc8c6ef552a8355c891a7f , < 8986c932905ea508d66da421eb2eb6e676ace1fe (git) Affected: 8d0bbc78046d264bbf6a574ea6f9072258a43e35 (git) Affected: b6a381c01e2ac98a48e32ac0f2a45bbadd9e26b0 (git) Affected: 5.10.261 , < 5.11 (semver) Affected: 5.15.212 , < 5.16 (semver)
Linux	Linux

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/client/smb2misc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "445ece263131780dee273d727a4d6f11934feec7",
              "status": "affected",
              "version": "31c6312608c60b72a1feb99a5afb680645a3e8a3",
              "versionType": "git"
            },
            {
              "lessThan": "36bfa52459e45c0d5b668de2f1c91f6dc5c67775",
              "status": "affected",
              "version": "573e502d14714d2947e22e7eff40ec20a6a44a42",
              "versionType": "git"
            },
            {
              "lessThan": "4a9d2657d3e05f6ed09c148cb127b4e58702275f",
              "status": "affected",
              "version": "419ec1b604d7fb60c10aec2dc062371f9fcd4940",
              "versionType": "git"
            },
            {
              "lessThan": "fdafa1e68dc75045b7b617e6e7d2854950804d83",
              "status": "affected",
              "version": "ceb875a375dedbf51c9425c1d13a2d7a8435c08c",
              "versionType": "git"
            },
            {
              "lessThan": "57cba95f0e97c6f6e45e6731da30aff091bd7460",
              "status": "affected",
              "version": "6e9d10f62773b99bd927940fd9cbdfe7207e23ff",
              "versionType": "git"
            },
            {
              "lessThan": "8986c932905ea508d66da421eb2eb6e676ace1fe",
              "status": "affected",
              "version": "53b7c271f06be4dd5cfc8c6ef552a8355c891a7f",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "8d0bbc78046d264bbf6a574ea6f9072258a43e35",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "b6a381c01e2ac98a48e32ac0f2a45bbadd9e26b0",
              "versionType": "git"
            },
            {
              "lessThan": "5.11",
              "status": "affected",
              "version": "5.10.261",
              "versionType": "semver"
            },
            {
              "lessThan": "5.16",
              "status": "affected",
              "version": "5.15.212",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/client/smb2misc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux"
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "5.10.261",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "5.15.212",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: reject overlapping data areas in SMB2 responses\n\nCommit 53b7c271f06b (\"smb: client: restrict implied bcc[0] exemption to\nresponses without data area\") restricted the implied bcc[0] length\nexception to responses without a data area. However, the overlap\nhandling in __smb2_calc_size() clears data_length, which can make an\ninvalid response appear to have no data area and so qualify for the\nexception.\n\nTrack data area overlap separately and reject such responses before\napplying the length compatibility exceptions."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.1,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - A malicious or compromised SMB server can deliver the crafted SMB2 response over TCP during client negotiation.\nAC:L - The overlapping offset and oversized length are attacker-controlled and deterministically bypass validation; no race or uncontrolled memory layout is required to trigger the out-of-bounds read.\nPR:N - The vulnerable NEGOTIATE response is processed before SMB authentication or signature verification, requiring no privileges or credentials on the target.\nUI:N - An already configured SMB mount can negotiate during automatic mounting or reconnection without a human opening crafted content.\nS:U - The vulnerable parser and the affected kernel memory remain within the Linux kernel\u0027s security authority.\nC:H - The validation mismatch permits an attacker-controlled ASN.1 length to read far beyond the 448-byte receive object, potentially traversing tens of kilobytes of adjacent kernel memory.\nI:N - The investigated paths provide an out-of-bounds read but no out-of-bounds write, use-after-free, type confusion, or other arbitrary modification primitive.\nA:H - The slab out-of-bounds access is repeatable and can produce a kernel fault or panic, particularly on hardened or memory-safety-instrumented deployments."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:52:09.787Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/445ece263131780dee273d727a4d6f11934feec7"
        },
        {
          "url": "https://git.kernel.org/stable/c/36bfa52459e45c0d5b668de2f1c91f6dc5c67775"
        },
        {
          "url": "https://git.kernel.org/stable/c/4a9d2657d3e05f6ed09c148cb127b4e58702275f"
        },
        {
          "url": "https://git.kernel.org/stable/c/fdafa1e68dc75045b7b617e6e7d2854950804d83"
        },
        {
          "url": "https://git.kernel.org/stable/c/57cba95f0e97c6f6e45e6731da30aff091bd7460"
        },
        {
          "url": "https://git.kernel.org/stable/c/8986c932905ea508d66da421eb2eb6e676ace1fe"
        }
      ],
      "title": "smb: client: reject overlapping data areas in SMB2 responses",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64257",
    "datePublished": "2026-07-25T08:49:09.345Z",
    "dateReserved": "2026-07-19T15:36:31.773Z",
    "dateUpdated": "2026-08-17T04:52:09.787Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

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.
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GHSA-CFRM-7RJV-HJ84

CVE-2026-64257 (GCVE-0-2026-64257)

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