FKIE_CVE-2026-31570
Vulnerability from fkie_nvd - Published: 2026-04-24 15:16 - Updated: 2026-04-27 20:33
Severity
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.
References
Impacted products
| Vendor | Product | Version | |
|---|---|---|---|
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | 5.4 | |
| linux | linux_kernel | 7.0 | |
| linux | linux_kernel | 7.0 | |
| linux | linux_kernel | 7.0 | |
| linux | linux_kernel | 7.0 | |
| linux | linux_kernel | 7.0 | |
| linux | linux_kernel | 7.0 | |
| linux | linux_kernel | 7.0 |
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"lang": "en",
"value": "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": "CVE-2026-31570",
"lastModified": "2026-04-27T20:33:16.367",
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"attackVector": "ADJACENT_NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 8.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 2.8,
"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"published": "2026-04-24T15:16:31.520",
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
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- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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