CVE-2026-31708 (GCVE-0-2026-31708)
Vulnerability from cvelistv5
Published
2026-05-01 13:56
Modified
2026-08-05 12:24
Severity ?
8.1 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: smb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path smb2_ioctl_query_info() has two response-copy branches: PASSTHRU_FSCTL and the default QUERY_INFO path. The QUERY_INFO branch clamps qi.input_buffer_length to the server-reported OutputBufferLength and then copies qi.input_buffer_length bytes from qi_rsp->Buffer to userspace, but it never verifies that the flexible-array payload actually fits within rsp_iov[1].iov_len. A malicious server can return OutputBufferLength larger than the actual QUERY_INFO response, causing copy_to_user() to walk past the response buffer and expose adjacent kernel heap to userspace. Guard the QUERY_INFO copy with a bounds check on the actual Buffer payload. Use struct_size(qi_rsp, Buffer, qi.input_buffer_length) rather than an open-coded addition so the guard cannot overflow on 32-bit builds.
References
Impacted products
Vendor Product Version
Linux Linux Version: f5778c398713692a16150ae96e5c8270bab8399f
Version: f5778c398713692a16150ae96e5c8270bab8399f
Version: f5778c398713692a16150ae96e5c8270bab8399f
Version: f5778c398713692a16150ae96e5c8270bab8399f
Version: f5778c398713692a16150ae96e5c8270bab8399f
Version: f5778c398713692a16150ae96e5c8270bab8399f
Version: f5778c398713692a16150ae96e5c8270bab8399f
Version: f5778c398713692a16150ae96e5c8270bab8399f
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/client/smb2ops.c"
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              "versionType": "original_commit_for_fix"
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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                  "versionStartIncluding": "5.1",
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path\n\nsmb2_ioctl_query_info() has two response-copy branches: PASSTHRU_FSCTL\nand the default QUERY_INFO path.  The QUERY_INFO branch clamps\nqi.input_buffer_length to the server-reported OutputBufferLength and then\ncopies qi.input_buffer_length bytes from qi_rsp-\u003eBuffer to userspace, but\nit never verifies that the flexible-array payload actually fits within\nrsp_iov[1].iov_len.\n\nA malicious server can return OutputBufferLength larger than the actual\nQUERY_INFO response, causing copy_to_user() to walk past the response\nbuffer and expose adjacent kernel heap to userspace.\n\nGuard the QUERY_INFO copy with a bounds check on the actual Buffer\npayload.  Use struct_size(qi_rsp, Buffer, qi.input_buffer_length)\nrather than an open-coded addition so the guard cannot overflow on\n32-bit builds."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The attacker-controlled data is an SMB2 QUERY_INFO response sent by a remote SMB server to the kernel SMB client over the network. The vulnerable copy is reached after the client issues the ioctl-triggered compound open/query/close request.\nAC:L - There is no race or fragile timing requirement; a malicious server controls the malformed response fields and can reliably make the advertised copy length exceed the actual response payload. CIFS/SMB client support is common and the affected SMB2+ path is not a rare configuration.\nPR:N - The malicious SMB server needs no privileges on the vulnerable client. The affected PASSTHRU_QUERY_INFO branch has no CAP_SYS_ADMIN check, unlike the FSCTL and SET_INFO branches.\nUI:R - A victim or local process must have mounted/accessed the SMB share and issued the CIFS_QUERY_INFO ioctl. The malicious server cannot reach this ioctl path entirely unsolicited.\nS:U - The impact is within the vulnerable kernel/client system security scope. This is not a VM escape, IOMMU bypass, or cross-authority boundary violation.\nC:H - The bug is an out-of-bounds kernel read copied to userspace from beyond the received SMB response buffer. The overread can expose adjacent kernel heap data and is not strictly bounded to only a few harmless bytes.\nI:N - The vulnerable operation is a read from kernel memory followed by copy_to_user. It does not provide a kernel write primitive or direct data modification.\nA:H - The same attacker-controlled length can drive copy_to_user far beyond the valid response buffer. That can trigger kernel faults or hardened usercopy failures, so a kernel crash is a defensible impact."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:24:43.143Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/e66bdc0704977ecee667a81d38255b579c2353d0"
        },
        {
          "url": "https://git.kernel.org/stable/c/9e203dbb5402897c43130fb171a2617008a91f45"
        },
        {
          "url": "https://git.kernel.org/stable/c/1dd757379997b71a328a4b591ffaf481acd0ead1"
        },
        {
          "url": "https://git.kernel.org/stable/c/a34d456934fe42e4da5d2cc07787bf418bee99c6"
        },
        {
          "url": "https://git.kernel.org/stable/c/ac2f14e4705d020f04e806efa0d49ab8dc2b145f"
        },
        {
          "url": "https://git.kernel.org/stable/c/078fae8f50adebb903ccf2252b44391324571e78"
        },
        {
          "url": "https://git.kernel.org/stable/c/85fd46ee26a11841c670449508025965f61ce131"
        },
        {
          "url": "https://git.kernel.org/stable/c/a58c5af19ff0d6f44f6e9fe31e33a2c92223f77e"
        }
      ],
      "title": "smb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31708",
    "datePublished": "2026-05-01T13:56:05.880Z",
    "dateReserved": "2026-03-09T15:48:24.132Z",
    "dateUpdated": "2026-08-05T12:24:43.143Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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