CVE-2026-31478 (GCVE-0-2026-31478)
Vulnerability from cvelistv5
Published
2026-04-22 13:54
Modified
2026-08-05 12:22
Severity ?
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len() After this commit (e2b76ab8b5c9 "ksmbd: add support for read compound"), response buffer management was changed to use dynamic iov array. In the new design, smb2_calc_max_out_buf_len() expects the second argument (hdr2_len) to be the offset of ->Buffer field in the response structure, not a hardcoded magic number. Fix the remaining call sites to use the correct offsetof() value.
References
Impacted products
Vendor Product Version
Linux Linux Version: f2283680a80571ca82d710bc6ecd8f8beac67d63
Version: 9f297df20d93411c0b4ddad7f88ba04a7cd36e77
Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: 5.15.145   ≤
Version: 6.1.71   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/smb2pdu.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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          ]
        },
        {
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          "product": "Linux",
          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.6"
            },
            {
              "lessThan": "6.6",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.203",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.168",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.131",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.80",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.21",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.11",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.203",
                  "versionStartIncluding": "5.15.145",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.168",
                  "versionStartIncluding": "6.1.71",
                  "vulnerable": true
                },
                {
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                  "versionEndExcluding": "6.12.80",
                  "versionStartIncluding": "6.6",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.21",
                  "versionStartIncluding": "6.6",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19.11",
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                  "vulnerable": true
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0",
                  "versionStartIncluding": "6.6",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len()\n\nAfter this commit (e2b76ab8b5c9 \"ksmbd: add support for read compound\"),\nresponse buffer management was changed to use dynamic iov array.\nIn the new design, smb2_calc_max_out_buf_len() expects the second\nargument (hdr2_len) to be the offset of -\u003eBuffer field in the\nresponse structure, not a hardcoded magic number.\nFix the remaining call sites to use the correct offsetof() value."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The vulnerable code is in ksmbd SMB2 request handling reachable over TCP SMB connections, including normal network-facing port 445 deployments.\nAC:L - An attacker controls the SMB2 compound request layout, output buffer lengths, and command sequence needed to reach the miscalculation; no race or external timing condition is required.\nPR:N - The handlers run after SMB session/tree setup, but ksmbd supports guest/anonymous sessions and guest shares, so a reasonable deployment allows a remote attacker to reach the path without credentials.\nUI:N - No victim action is required after the ksmbd service is exposed; the attacker sends crafted SMB2 requests directly.\nS:U - The impact remains within the kernel/ksmbd security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - The bug can cause out-of-bounds kernel response-buffer memory corruption in compound SMB2 handling, which is defensibly treatable as exploitable memory corruption with potential information disclosure.\nI:H - The incorrect length calculation can permit an out-of-bounds write past the ksmbd response buffer, and kernel OOB writes are scored as high integrity impact.\nA:H - Even if not weaponized for code execution, the out-of-bounds kernel write can crash or oops the kernel, causing high availability impact."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:22:57.123Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/70b4c414889492c522b6e4331562360f49be2361"
        },
        {
          "url": "https://git.kernel.org/stable/c/9a7166f0ef8cbb7bb48dd05e2471d995566003f5"
        },
        {
          "url": "https://git.kernel.org/stable/c/c3a89e3ec1ccf64fa6a34e391e1581ebbcba8683"
        },
        {
          "url": "https://git.kernel.org/stable/c/6aef1765d6807e0f027cd87f6ac973eb0879a46d"
        },
        {
          "url": "https://git.kernel.org/stable/c/80824c7e527b70cf9039534e60aff592e8f209d1"
        },
        {
          "url": "https://git.kernel.org/stable/c/4cb537ae4f37d7d0f617815ed4bed7173fb50861"
        },
        {
          "url": "https://git.kernel.org/stable/c/0e55f63dd08f09651d39e1b709a91705a8a0ddcb"
        }
      ],
      "title": "ksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31478",
    "datePublished": "2026-04-22T13:54:06.157Z",
    "dateReserved": "2026-03-09T15:48:24.098Z",
    "dateUpdated": "2026-08-05T12:22:57.123Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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