CVE-2021-4454

MEDIUMNVD 5.55.5—
EchelonGraph scoreMEDIUM confidence

Score 5.5 from GitHub Security Advisory published 2025-03-27. NVD baseline CVSS 5.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 3 sources updated this week
5.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 5.5Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

In the Linux kernel, the following vulnerability has been resolved:

can: j1939: fix errant WARN_ON_ONCE in j1939_session_deactivate

The conclusion "j1939_session_deactivate() should be called with a session ref-count of at least 2" is incorrect. In some concurrent scenarios, j1939_session_deactivate can be called with the session ref-count less than 2. But there is not any problem because it will check the session active state before session putting in j1939_session_deactivate_locked().

Here is the concurrent scenario of the problem reported by syzbot and my reproduction log.

cpu0 cpu1 j1939_xtp_rx_eoma j1939_xtp_rx_abort_one j1939_session_get_by_addr [kref == 2] j1939_session_get_by_addr [kref == 3] j1939_session_deactivate [kref == 2] j1939_session_put [kref == 1] j1939_session_completed j1939_session_deactivate WARN_ON_ONCE(kref < 2)

===================================================== WARNING: CPU: 1 PID: 21 at net/can/j1939/transport.c:1088 j1939_session_deactivate+0x5f/0x70 CPU: 1 PID: 21 Comm: ksoftirqd/1 Not tainted 5.14.0-rc7+ #32 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/2014 RIP: 0010:j1939_session_deactivate+0x5f/0x70 Call Trace: j1939_session_deactivate_activate_next+0x11/0x28 j1939_xtp_rx_eoma+0x12a/0x180 j1939_tp_recv+0x4a2/0x510 j1939_can_recv+0x226/0x380 can_rcv_filter+0xf8/0x220 can_receive+0x102/0x220 ? process_backlog+0xf0/0x2c0 can_rcv+0x53/0xf0 __netif_receive_skb_one_core+0x67/0x90 ? process_backlog+0x97/0x2c0 __netif_receive_skb+0x22/0x80

CVSS v3
5.5
EG Score
5.5(medium)
EG Risk
29(Track)
EG Risk 29/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity55% × 45%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
43%
KEV
Not listed

Published

March 27, 2025

Last Modified

August 5, 2026

References (5)

Data Freshness Timeline

(refreshed 13× in last 7d / 45× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 117 total refreshes for this CVE.

  1. 2026-08-07 16:24 UTCEPSS rescore
  2. 2026-08-06 13:44 UTCEPSS rescore
  3. 2026-08-05 19:15 UTCEPSS rescore
  4. 2026-08-05 09:31 UTCEG score recompute
  5. 2026-08-05 09:31 UTCGHSA enrichment
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  7. 2026-08-04 11:06 UTCEG score recompute
  8. 2026-08-04 11:06 UTCGHSA enrichment
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  11. 2026-08-04 09:45 UTCGHSA enrichment
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  24. 2026-07-23 02:05 UTCEG score recompute
  25. 2026-07-22 22:51 UTCEG score recompute
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Frequently asked(5)

What is CVE-2021-4454?
CVE-2021-4454 is a medium vulnerability published on March 27, 2025. In the Linux kernel, the following vulnerability has been resolved: can: j1939: fix errant WARNONONCE in j1939sessiondeactivate The conclusion "j1939sessiondeactivate() should be called with a session ref-count of at least 2" is incorrect. In some concurrent scenarios, j1939sessiondeactivate can be…
When was CVE-2021-4454 disclosed?
CVE-2021-4454 was first published in the National Vulnerability Database on March 27, 2025, with the most recent update on August 5, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-4454 actively exploited?
CVE-2021-4454 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 57.2% of all scored CVEs.
What is the CVSS score of CVE-2021-4454?
CVE-2021-4454 has a CVSS v3 base score of 5.5 (NVD).
How do I remediate CVE-2021-4454?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-4454, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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