CVE-2021-4454Network attack vector

Service interruption via erroneous J1939 refcount warning

Published Mar 27, 2025 · Updated Aug 5, 2026

Denial of service in the Linux kernel's J1939 CAN transport allows remote attackers to interrupt service through concurrent teardown. The j1939_session_deactivate function treats a valid session reference count below two as an invariant violation and invokes WARN_ON_ONCE during overlapping EOMA and abort processing. Concurrent J1939 traffic is required, and systems configured to panic on kernel warnings can crash rather than merely log the erroneous warning.

CVSS severity7.5
High
EPSS probability0.57%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in the Linux kernel's J1939 CAN transport allows remote attackers to interrupt service through concurrent teardown. The j1939_session_deactivate function treats a valid session reference count below two as an invariant violation and invokes WARN_ON_ONCE during overlapping EOMA and abort processing. Concurrent J1939 traffic is required, and systems configured to panic on kernel warnings can crash rather than merely log the erroneous warning.

The record

CVE
CVE-2021-4454
Published
Mar 27, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 27, 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=0c71437dd50dd687c15d8ca80b3b68f10bb21d63 <1740a1e45eee65099a92fb502e1e67e63aad277d
  2. Affected versionversion=0c71437dd50dd687c15d8ca80b3b68f10bb21d63 <9ab896775f98ff54b68512f345eed178bf961084
  3. Affected versionversion=0c71437dd50dd687c15d8ca80b3b68f10bb21d63 <d0553680f94c49bbe0e39eb50d033ba563b4212d
  4. Affected versionversion=5.10.56 <5.10.168
  5. Affected versionversion=5.13.8 <5.14
  6. Affected versionversion=5.14
  7. Affected versionversion=5.4.138 <5.4.232
  8. Affected versionversion=55dd22c5d029423f513fd849e633adf0e9c10d0c <b6d44072117bba057d50f7a2f96e5d070c65926d
  9. Affected versionversion=5e1fc537c1be332aef9621ca9146aeb3ba59522f
  10. Affected versionversion=7eef18c0479ba5d9f54fba30cd77c233ebca3eb1 <6950df42a03c9ac9290503ced3f371199cb68fa9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=0c71437dd50dd687c15d8ca80b3b68f10bb21d63 <1740a1e45eee65099a92fb502e1e67e63aad277d; version=0c71437dd50dd687c15d8ca80b3b68f10bb21d63 <9ab896775f98ff54b68512f345eed178bf961084; version=0c71437dd50dd687c15d8ca80b3b68f10bb21d63 <d0553680f94c49bbe0e39eb50d033ba563b4212d; version=5.10.56 <5.10.168; version=5.13.8 <5.14; version=5.14; version=5.4.138 <5.4.232; version=55dd22c5d029423f513fd849e633adf0e9c10d0c <b6d44072117bba057d50f7a2f96e5d070c65926d; version=5e1fc537c1be332aef9621ca9146aeb3ba59522f; version=7eef18c0479ba5d9f54fba30cd77c233ebca3eb1 <6950df42a03c9ac9290503ced3f371199cb68fa9

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.5kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.5UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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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