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CVE-2021-47668: can: dev: can_restart: fix use after free bug

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-04-17 · updated 2026-08-04
• Weakness: CWE-416

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.

Affected products

• Linux kernel: from 2.6.31 before 4.4.254; from 4.5 before 4.9.254; from 4.10 before 4.14.218; from 4.15 before 4.19.171; from 4.20 before 5.4.93; from 5.5 before 5.10.11 — fixed in 4.14.218, 4.19.171, 4.4.254, 4.9.254, 5.10.11, 5.4.93

How to fix

Upgrade to a fixed version: Linux kernel 4.14.218, 4.19.171, 4.4.254, 4.9.254. Check the vendor advisory for mitigations.

References

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

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