CVE-2026-31432 (GCVE-0-2026-31432)
Vulnerability from cvelistv5
Published
2026-04-22 08:15
Modified
2026-08-05 12:22
Severity ?
8.8 (High) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix OOB write in QUERY_INFO for compound requests When a compound request such as READ + QUERY_INFO(Security) is received, and the first command (READ) consumes most of the response buffer, ksmbd could write beyond the allocated buffer while building a security descriptor. The root cause was that smb2_get_info_sec() checked buffer space using ppntsd_size from xattr, while build_sec_desc() often synthesized a significantly larger descriptor from POSIX ACLs. This patch introduces smb_acl_sec_desc_scratch_len() to accurately compute the final descriptor size beforehand, performs proper buffer checking with smb2_calc_max_out_buf_len(), and uses exact-sized allocation + iov pinning.
References
Impacted products
Vendor Product Version
Linux Linux Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d
Version: f2283680a80571ca82d710bc6ecd8f8beac67d63
Version: 9f297df20d93411c0b4ddad7f88ba04a7cd36e77
Version: 5.15.145   ≤
Version: 6.1.71   ≤
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix OOB write in QUERY_INFO for compound requests\n\nWhen a compound request such as READ + QUERY_INFO(Security) is received,\nand the first command (READ) consumes most of the response buffer,\nksmbd could write beyond the allocated buffer while building a security\ndescriptor.\n\nThe root cause was that smb2_get_info_sec() checked buffer space using\nppntsd_size from xattr, while build_sec_desc() often synthesized a\nsignificantly larger descriptor from POSIX ACLs.\n\nThis patch introduces smb_acl_sec_desc_scratch_len() to accurately\ncompute the final descriptor size beforehand, performs proper buffer\nchecking with smb2_calc_max_out_buf_len(), and uses exact-sized\nallocation + iov pinning."
        }
      ],
      "metrics": [
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          "cvssV3_1": {
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
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              "value": "AV:N - ksmbd is the in-kernel SMB server listening on TCP/445, directly reachable over the network by any remote SMB client.\nAC:L - The attacker reliably triggers the OOB write by crafting a compound request (e.g., READ + QUERY_INFO(Security)) where the first command consumes most of the response buffer. No race condition or special conditions are needed.\nPR:L - The QUERY_INFO command requires a valid SMB session (checked by smb2_check_user_session), a tree connect, and an open file handle. Even guest access requires completing session setup, so low privileges are needed.\nUI:N - No user interaction is required; the attacker sends the compound request directly to the ksmbd server.\nS:U - The vulnerability results in kernel heap corruption within the same security authority (the kernel); no security boundary such as a VM or sandbox is crossed.\nC:H - The heap buffer overflow writes past the kvzalloc\u0027d response buffer into adjacent kernel heap objects. This OOB write can be leveraged to corrupt adjacent structures and create information disclosure primitives.\nI:H - The OOB write corrupts kernel heap memory with attacker-influenced data (security descriptor content including SIDs and ACEs derived from file ACLs), enabling potential control flow hijacking or arbitrary write primitives.\nA:H - The heap buffer overflow corrupts adjacent kernel data structures, reliably causing kernel crashes or panics."
            }
          ]
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      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:22:26.699Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/850452af77f55d185f9445e1f7a1db53c5e4aad4"
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          "url": "https://git.kernel.org/stable/c/d48c64fb80ad78b3dd29fb7d79b6ec7bd72bfc09"
        },
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          "url": "https://git.kernel.org/stable/c/075ea208c648cc2bcd616295b711d3637c61de45"
        },
        {
          "url": "https://git.kernel.org/stable/c/515c2daab46021221bdf406bef19bc90a44ec617"
        },
        {
          "url": "https://git.kernel.org/stable/c/fda9522ed6afaec45cabc198d8492270c394c7bc"
        }
      ],
      "title": "ksmbd: fix OOB write in QUERY_INFO for compound requests",
      "x_generator": {
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31432",
    "datePublished": "2026-04-22T08:15:10.873Z",
    "dateReserved": "2026-03-09T15:48:24.089Z",
    "dateUpdated": "2026-08-05T12:22:26.699Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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