CVE-2026-97563 (GCVE-0-2026-97563)

Vulnerability from cvelistv5 – Published: 2026-09-25 10:21 – Updated: 2026-09-25 10:21
VLAI
Title
smb: client: reject out-of-bounds DataOffset in CIFSSMBRead()
Summary
In the Linux kernel, the following vulnerability has been resolved: smb: client: reject out-of-bounds DataOffset in CIFSSMBRead() The SMB1 synchronous read helper CIFSSMBRead() validates the server's DataLength against CIFSMaxBufSize and the caller's count, but never validates DataOffset. The copy source is formed as &pSMBr->hdr.Protocol + le16_to_cpu(pSMBr->DataOffset) and memcpy()'d for DataLength bytes with no check that the [DataOffset, DataOffset + DataLength) range lies within the response actually received from the server. A malicious or compromised SMB1 server can return a response carrying an in-range DataLength and a large DataOffset, driving the source pointer past the end of the response buffer. The memcpy() then copies adjacent kernel heap into the caller's read buffer (information disclosure), or reads unmapped memory and oopses (denial of service). SMB1 is not negotiated by default; reaching this code requires an explicit vers=1.0 mount. Both DataOffset and the received response length recorded in rsp_iov.iov_len are relative to the start of the SMB header, so reject the response unless DataOffset + DataLength fits within that length, using overflow-safe arithmetic, before forming the source pointer. The response length has been validated by the previous patch, so the DataOffset and DataLength fields can be read safely here. While here, make data_length unsigned. It holds a length derived from unsigned on-the-wire fields and is only ever compared against unsigned quantities; print it with %u accordingly, and add __func__ to the cifs_dbg() calls in this function.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 667feba13e78d16393aacb15869f70970f422227 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 5be5bdda5863eacc964b609ba927764f253431b3 (git)
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Linux Linux Affected: 2.6.12
Unaffected: 0 , < 2.6.12 (semver)
Unaffected: 7.2.7 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc3 , ≤ * (original_commit_for_fix)
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{
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      "affected": [
        {
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          "product": "Linux",
          "programFiles": [
            "fs/smb/client/cifssmb.c",
            "fs/smb/client/trace.h"
          ],
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: reject out-of-bounds DataOffset in CIFSSMBRead()\n\nThe SMB1 synchronous read helper CIFSSMBRead() validates the server\u0027s\nDataLength against CIFSMaxBufSize and the caller\u0027s count, but never\nvalidates DataOffset. The copy source is formed as\n\n\t\u0026pSMBr-\u003ehdr.Protocol + le16_to_cpu(pSMBr-\u003eDataOffset)\n\nand memcpy()\u0027d for DataLength bytes with no check that the\n[DataOffset, DataOffset + DataLength) range lies within the response\nactually received from the server.\n\nA malicious or compromised SMB1 server can return a response carrying\nan in-range DataLength and a large DataOffset, driving the source\npointer past the end of the response buffer. The memcpy() then copies\nadjacent kernel heap into the caller\u0027s read buffer (information\ndisclosure), or reads unmapped memory and oopses (denial of service).\nSMB1 is not negotiated by default; reaching this code requires an\nexplicit vers=1.0 mount.\n\nBoth DataOffset and the received response length recorded in\nrsp_iov.iov_len are relative to the start of the SMB header, so reject\nthe response unless DataOffset + DataLength fits within that length,\nusing overflow-safe arithmetic, before forming the source pointer.\nThe response length has been validated by the previous patch, so the\nDataOffset and DataLength fields can be read safely here.\n\nWhile here, make data_length unsigned. It holds a length derived from\nunsigned on-the-wire fields and is only ever compared against unsigned\nquantities; print it with %u accordingly, and add __func__ to the\ncifs_dbg() calls in this function."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-25T10:21:51.261Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/667feba13e78d16393aacb15869f70970f422227"
        },
        {
          "url": "https://git.kernel.org/stable/c/5be5bdda5863eacc964b609ba927764f253431b3"
        }
      ],
      "title": "smb: client: reject out-of-bounds DataOffset in CIFSSMBRead()",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-97563",
    "datePublished": "2026-09-25T10:21:51.261Z",
    "dateReserved": "2026-09-24T16:01:01.155Z",
    "dateUpdated": "2026-09-25T10:21:51.261Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-10-02",
      "epss": "0.00189",
      "percentile": "0.07731"
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        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: reject out-of-bounds DataOffset in CIFSSMBRead()\n\nThe SMB1 synchronous read helper CIFSSMBRead() validates the server\u0027s\nDataLength against CIFSMaxBufSize and the caller\u0027s count, but never\nvalidates DataOffset. The copy source is formed as\n\n\t\u0026pSMBr-\u003ehdr.Protocol + le16_to_cpu(pSMBr-\u003eDataOffset)\n\nand memcpy()\u0027d for DataLength bytes with no check that the\n[DataOffset, DataOffset + DataLength) range lies within the response\nactually received from the server.\n\nA malicious or compromised SMB1 server can return a response carrying\nan in-range DataLength and a large DataOffset, driving the source\npointer past the end of the response buffer. The memcpy() then copies\nadjacent kernel heap into the caller\u0027s read buffer (information\ndisclosure), or reads unmapped memory and oopses (denial of service).\nSMB1 is not negotiated by default; reaching this code requires an\nexplicit vers=1.0 mount.\n\nBoth DataOffset and the received response length recorded in\nrsp_iov.iov_len are relative to the start of the SMB header, so reject\nthe response unless DataOffset + DataLength fits within that length,\nusing overflow-safe arithmetic, before forming the source pointer.\nThe response length has been validated by the previous patch, so the\nDataOffset and DataLength fields can be read safely here.\n\nWhile here, make data_length unsigned. It holds a length derived from\nunsigned on-the-wire fields and is only ever compared against unsigned\nquantities; print it with %u accordingly, and add __func__ to the\ncifs_dbg() calls in this function."
          }
        ],
        "id": "CVE-2026-97563",
        "lastModified": "2026-09-25T11:17:06.883",
        "metrics": {},
        "published": "2026-09-25T11:17:06.883",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "vulnStatus": "Received"
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      "cve": "CVE-2026-97563",
      "id": "CVE-2026-97563",
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      "product_status:known_affected": "234",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: smb: client: reject out-of-bounds DataOffset in CIFSSMBRead()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97563.json",
      "version": "3"
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      "id": "CVE-2026-97563",
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      "title": "SUSE CVE CVE-2026-97563",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-97563.json",
      "version": "2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • 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.
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  • 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.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.