can: gw: fix OOB heap access in cgw_csum_crc8_rel()

{
  "id": "891f067ab9e97687dcbe7d9c59dbaa060868d6dd10adf080df6dac42ee9546d9",
  "url": "https://osv.dev/vulnerability/CVE-2026-31570",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "can: gw: fix OOB heap access in cgw_csum_crc8_rel()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: can: gw: fix OOB heap access in cgw_csum_crc8_rel() cgw_csum_crc8_rel() correctly computes bounds-safe indices via calc_idx(): int from = calc_idx(crc8->from_idx, cf->len); int to = calc_idx(crc8->to_idx, cf->len); int res = calc_idx(crc8->result_idx, cf->len); if (from < 0 || to < 0 || res < 0) return; However, the loop and the result write then use the raw s8 fields directly instead of the computed variables: for (i = crc8->from_idx; ...) /* BUG: raw negative index */ cf->data[crc8->result_idx] = ...; /* BUG: raw negative index */ With from_idx = to_idx = result_idx = -64 on a 64-byte CAN FD frame, calc_idx(-64, 64) = 0 so the guard passes, but the loop iterates with i = -64, reading cf->data[-64], and the write goes to cf->data[-64]. This write might end up to 56 (7.0-rc) or 40 (<= 6.19) bytes before the start of the canfd_frame on the heap. The companion function cgw_csum_xor_rel() uses `from`/`to`/`res` correctly throughout; fix cgw_csum_crc8_rel() to match. Confirmed with KASAN on linux-7.0-rc2: BUG: KASAN: slab-out-of-bounds in cgw_csum_crc8_rel+0x515/0x5b0 Read of size 1 at addr ffff8880076619c8 by task poc_cgw_oob/62 To configure the can-gw crc8 checksums CAP_NET_ADMIN is needed.",
    "evidence": "osv:CVE-2026-31570",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.253",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.203",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.168",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.131",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.80",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.21",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.11",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-31570",
      "aliases": [
        "CVE-2026-31570"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
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              "type": "GIT",
              "events": [
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                  "fixed": "999ca48d55a8a46da21519db7e834e5867200379"
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                  "fixed": "a025283d7f7404c739225e457fb99db2368bb544"
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31570.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.4.0"
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                {
                  "fixed": "5.10.253"
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              "type": "ECOSYSTEM",
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              "type": "ECOSYSTEM",
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                  "introduced": "6.7.0"
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            {
              "type": "ECOSYSTEM",
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          "package": {
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            "ecosystem": "Linux"
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      ],
      "modified": "2026-10-28T02:30:24.808978086Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/54ecdf76a55e75c1f5085e440f8ab671a3283ef5",
        "https://git.kernel.org/stable/c/66b689efd08227da2c5ca49b58b30a95d23c695a",
        "https://git.kernel.org/stable/c/84f8b76d24273175a22713e83e90874e1880d801",
        "https://git.kernel.org/stable/c/999ca48d55a8a46da21519db7e834e5867200379",
        "https://git.kernel.org/stable/c/a025283d7f7404c739225e457fb99db2368bb544",
        "https://git.kernel.org/stable/c/b9c310d72783cc2f30d103eed83920a5a29c671a",
        "https://git.kernel.org/stable/c/c4e8eaa75fa0b6bcbfa5356d6195c4ad0e05e57a",
        "https://git.kernel.org/stable/c/e7c99348b0612b2bc02d5ce6ff9873261cc7605f",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31570.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-31570",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31570.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-31570",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 491580,
  "published_at": "2026-04-24T14:35:49.435+00:00"
}