CVE-2026-31705 (GCVE-0-2026-31705)
Vulnerability from cvelistv5
Published
2026-05-01 13:56
Modified
2026-05-03 05:45
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: fix out-of-bounds write in smb2_get_ea() EA alignment smb2_get_ea() applies 4-byte alignment padding via memset() after writing each EA entry. The bounds check on buf_free_len is performed before the value memcpy, but the alignment memset fires unconditionally afterward with no check on remaining space. When the EA value exactly fills the remaining buffer (buf_free_len == 0 after value subtraction), the alignment memset writes 1-3 NUL bytes past the buf_free_len boundary. In compound requests where the response buffer is shared across commands, the first command (e.g., READ) can consume most of the buffer, leaving a tight remainder for the QUERY_INFO EA response. The alignment memset then overwrites past the physical kvmalloc allocation into adjacent kernel heap memory. Add a bounds check before the alignment memset to ensure buf_free_len can accommodate the padding bytes. This is the same bug pattern fixed by commit beef2634f81f ("ksmbd: fix potencial OOB in get_file_all_info() for compound requests") and commit fda9522ed6af ("ksmbd: fix OOB write in QUERY_INFO for compound requests"), both of which added bounds checks before unconditional writes in QUERY_INFO response handlers.
References
Impacted products
Vendor Product Version
Linux Linux Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: f2283680a80571ca82d710bc6ecd8f8beac67d63
Version: 9f297df20d93411c0b4ddad7f88ba04a7cd36e77
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{
  "containers": {
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          "programFiles": [
            "fs/smb/server/smb2pdu.c"
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      "cpeApplicability": [
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          "nodes": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment\n\nsmb2_get_ea() applies 4-byte alignment padding via memset() after\nwriting each EA entry. The bounds check on buf_free_len is performed\nbefore the value memcpy, but the alignment memset fires unconditionally\nafterward with no check on remaining space.\n\nWhen the EA value exactly fills the remaining buffer (buf_free_len == 0\nafter value subtraction), the alignment memset writes 1-3 NUL bytes\npast the buf_free_len boundary. In compound requests where the response\nbuffer is shared across commands, the first command (e.g., READ) can\nconsume most of the buffer, leaving a tight remainder for the QUERY_INFO\nEA response. The alignment memset then overwrites past the physical\nkvmalloc allocation into adjacent kernel heap memory.\n\nAdd a bounds check before the alignment memset to ensure buf_free_len\ncan accommodate the padding bytes.\n\nThis is the same bug pattern fixed by commit beef2634f81f (\"ksmbd: fix\npotencial OOB in get_file_all_info() for compound requests\") and\ncommit fda9522ed6af (\"ksmbd: fix OOB write in QUERY_INFO for compound\nrequests\"), both of which added bounds checks before unconditional\nwrites in QUERY_INFO response handlers."
        }
      ],
      "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"
          }
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-03T05:45:28.481Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/ffbce350c6fd1e99116ea57383b9031717e36d3b"
        },
        {
          "url": "https://git.kernel.org/stable/c/98f3de6ef4efbd899348d333f0902dc4ff14380c"
        },
        {
          "url": "https://git.kernel.org/stable/c/790304c02bf9bd7b8171feda4294d6e62d32ae8f"
        },
        {
          "url": "https://git.kernel.org/stable/c/922d48fe8c19f388ffa2f709f33acaae4e408de2"
        },
        {
          "url": "https://git.kernel.org/stable/c/30010c952077a1c89ecdd71fc4d574c75a8f5617"
        }
      ],
      "title": "ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment",
      "x_generator": {
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    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31705",
    "datePublished": "2026-05-01T13:56:03.896Z",
    "dateReserved": "2026-03-09T15:48:24.132Z",
    "dateUpdated": "2026-05-03T05:45:28.481Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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