CVE-2021-47232Network attack vector

Memory corruption via unreferenced J1939 session skb

Published May 21, 2024 · Updated Aug 5, 2026

Use-after-free in the Linux Kernel J1939 transport subsystem allows attackers to corrupt kernel memory by racing CTS processing. The session queue lookup in net/can/j1939/transport.c returns an sk_buff without incrementing its reference count, so concurrent CTS-driven removal frees the buffer while callers still use it. Reachability requires an active J1939 transport session and either an unauthenticated CAN peer or an unprivileged local AF_CAN socket; successful reuse permits kernel-memory reads or writes, while dereference can panic the system.

CVSS severity9.8
Critical
EPSS probability0.62%
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 Kernel J1939 transport subsystem allows attackers to corrupt kernel memory by racing CTS processing. The session queue lookup in net/can/j1939/transport.c returns an sk_buff without incrementing its reference count, so concurrent CTS-driven removal frees the buffer while callers still use it. Reachability requires an active J1939 transport session and either an unauthenticated CAN peer or an unprivileged local AF_CAN socket; successful reuse permits kernel-memory reads or writes, while dereference can panic the system.

The record

CVE
CVE-2021-47232
Published
May 21, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1068, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 21, 2024CVE 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=5.4
  2. Affected versionversion=9d71dd0c70099914fcd063135da3c580865e924c <1071065eeb33d32b7d98c2ce7591881ae7381705
  3. Affected versionversion=9d71dd0c70099914fcd063135da3c580865e924c <2030043e616cab40f510299f09b636285e0a3678
  4. Affected versionversion=9d71dd0c70099914fcd063135da3c580865e924c <22cba878abf646cd3a02ee7c8c2cef7afe66a256
  5. Affected versionversion=9d71dd0c70099914fcd063135da3c580865e924c <509ab6bfdd0c76daebbad0f0af07da712116de22

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.4; version=9d71dd0c70099914fcd063135da3c580865e924c <1071065eeb33d32b7d98c2ce7591881ae7381705; version=9d71dd0c70099914fcd063135da3c580865e924c <2030043e616cab40f510299f09b636285e0a3678; version=9d71dd0c70099914fcd063135da3c580865e924c <22cba878abf646cd3a02ee7c8c2cef7afe66a256; version=9d71dd0c70099914fcd063135da3c580865e924c <509ab6bfdd0c76daebbad0f0af07da712116de22
The Linux Kernel Organization · Linux Kernelversion=5.4; version=9d71dd0c7009 <1071065eeb33; version=9d71dd0c7009 <2030043e616c; version=9d71dd0c7009 <22cba878abf6; version=9d71dd0c7009 <509ab6bfdd0c

Published CVSS scores

9.8Linux CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
8.4CISA ADPCVSS:3.1/AV:L/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

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

Weakness, pattern, technique

CWE-416Use After Free
T1068Exploitation for Privilege Escalation
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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