CVE-2021-47668

Kernel compromise via freed CAN frame access

Published Apr 17, 2025 · Updated Aug 5, 2026

Use-after-free in the Linux CAN restart path allows adjacent attackers to crash or compromise affected kernels through CAN bus errors. In drivers/net/can/dev.c, can_restart calls netif_rx_ni(skb), which can free the socket buffer, before reading cf->len from its aliased CAN frame. Reachability requires access to the same CAN segment and automatic bus-off recovery; forced bus-off invokes the faulty restart path without a host account.

CVSS severity8.8
High
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the Linux CAN restart path allows adjacent attackers to crash or compromise affected kernels through CAN bus errors. In drivers/net/can/dev.c, can_restart calls netif_rx_ni(skb), which can free the socket buffer, before reading cf->len from its aliased CAN frame. Reachability requires access to the same CAN segment and automatic bus-off recovery; forced bus-off invokes the faulty restart path without a host account.

The record

CVE
CVE-2021-47668
Published
Apr 17, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1499
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 17, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.6.31
  2. Affected versionversion=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <03f16c5075b22c8902d2af739969e878b0879c94
  3. Affected versionversion=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <08ab951787098ae0b6c0364aeea7a8138226f234
  4. Affected versionversion=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <260925a0b7d2da5449f8ecfd02c1405e0c8a45b8
  5. Affected versionversion=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <593c072b7b3c4d7044416eb039d9ad706bedd67a
  6. Affected versionversion=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <92668d28c7e6a7a2ba07df287669ffcdf650c421
  7. Affected versionversion=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <ac48ef15826e83f4206c47add61072e8fc76d328
  8. Affected versionversion=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <bbc6847b9b8978b520f62fbc7c68c54ef0f8d282

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.31; version=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <03f16c5075b22c8902d2af739969e878b0879c94; version=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <08ab951787098ae0b6c0364aeea7a8138226f234; version=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <260925a0b7d2da5449f8ecfd02c1405e0c8a45b8; version=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <593c072b7b3c4d7044416eb039d9ad706bedd67a; version=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <92668d28c7e6a7a2ba07df287669ffcdf650c421; version=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <ac48ef15826e83f4206c47add61072e8fc76d328; version=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <bbc6847b9b8978b520f62fbc7c68c54ef0f8d282

Published CVSS scores

7.8CISA ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
8.8Linux Kernel CNACVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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