GHSA-67VP-4P2P-JR3C

Vulnerability from github – Published: 2026-04-24 15:32 – Updated: 2026-04-24 15:32
VLAI?
Details

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.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-31570"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-04-24T15:16:31Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncan: gw: fix OOB heap access in cgw_csum_crc8_rel()\n\ncgw_csum_crc8_rel() correctly computes bounds-safe indices via calc_idx():\n\n    int from = calc_idx(crc8-\u003efrom_idx, cf-\u003elen);\n    int to   = calc_idx(crc8-\u003eto_idx,   cf-\u003elen);\n    int res  = calc_idx(crc8-\u003eresult_idx, cf-\u003elen);\n\n    if (from \u003c 0 || to \u003c 0 || res \u003c 0)\n        return;\n\nHowever, the loop and the result write then use the raw s8 fields directly\ninstead of the computed variables:\n\n    for (i = crc8-\u003efrom_idx; ...)        /* BUG: raw negative index */\n    cf-\u003edata[crc8-\u003eresult_idx] = ...;    /* BUG: raw negative index */\n\nWith from_idx = to_idx = result_idx = -64 on a 64-byte CAN FD frame,\ncalc_idx(-64, 64) = 0 so the guard passes, but the loop iterates with\ni = -64, reading cf-\u003edata[-64], and the write goes to cf-\u003edata[-64].\nThis write might end up to 56 (7.0-rc) or 40 (\u003c= 6.19) bytes before the\nstart of the canfd_frame on the heap.\n\nThe companion function cgw_csum_xor_rel() uses `from`/`to`/`res`\ncorrectly throughout; fix cgw_csum_crc8_rel() to match.\n\nConfirmed with KASAN on linux-7.0-rc2:\n  BUG: KASAN: slab-out-of-bounds in cgw_csum_crc8_rel+0x515/0x5b0\n  Read of size 1 at addr ffff8880076619c8 by task poc_cgw_oob/62\n\nTo configure the can-gw crc8 checksums CAP_NET_ADMIN is needed.",
  "id": "GHSA-67vp-4p2p-jr3c",
  "modified": "2026-04-24T15:32:34Z",
  "published": "2026-04-24T15:32:34Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31570"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/54ecdf76a55e75c1f5085e440f8ab671a3283ef5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/66b689efd08227da2c5ca49b58b30a95d23c695a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/84f8b76d24273175a22713e83e90874e1880d801"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/999ca48d55a8a46da21519db7e834e5867200379"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a025283d7f7404c739225e457fb99db2368bb544"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b9c310d72783cc2f30d103eed83920a5a29c671a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c4e8eaa75fa0b6bcbfa5356d6195c4ad0e05e57a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e7c99348b0612b2bc02d5ce6ff9873261cc7605f"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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