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Vulnerabilities

Vulnerability · CVE-2021-4454

can: j1939: fix errant WARN_ON_ONCE in j1939_session_deactivate

Published Mar 27, 2025 · catalog updated Oct 16, 2026 · Linux Linux

Check if you run it

No confirmed exploitation is on record for CVE-2021-4454. EPSS is 0.58%. Act only if a listed version of Linux Linux is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.58%
Remediation
Advisory link
Affected products
Debian:12 linux · Debian:13 linux · Debian:14 linux · cpe linux/linux kernel · vendor Linux Linux

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

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Debian:12 linux0 → 6.1.11-1
  • Debian:13 linux0 → 6.1.11-1
  • Debian:14 linux0 → 6.1.11-1
  • cpe linux/linux kernel5.14
  • vendor Linux Linuxversion unspecified

How to fix CVE-2021-4454

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2021-4454. EPSS is 0.58%. Act only if a listed version of Linux Linux is installed.

Which versions are affected?

Compare what you have installed with linux/linux kernel 5.14. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.58%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Debian security

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 27, 2025 · CIRCL Vulnerability Lookup

    Detected

    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

  2. Oct 15, 2026 · CIRCL Vulnerability Lookup

    Updated

    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

  3. Oct 15, 2026 · NIST NVD

    Updated

    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

  4. Oct 16, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    linux fixed in 6.1.11-1; linux fixed in 6.1.11-1; linux fixed in 6.1.11-1

  5. Oct 16, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    linux fixed in 6.1.11-1

  6. Oct 16, 2026 · OpenSSF OSV / OSV Scanner

    Updated

    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

Sources

  • CIRCL Vulnerability LookupVulnerability recordCVE-2021-4454

    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, j193

    vulnerability.circl.lu
  • CVE.orgVulnerability recordCVE-2021-4454

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-4454

    30-day exploitation probability 0.6%

    first.org
  • NIST NVDVulnerability recordCVE-2021-4454

    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, j1

    nvd.nist.gov
  • OpenSSF OSV / OSV ScannerPackage advisoryDEBIAN-CVE-2021-4454
    osv.dev

References

Freshness

Last verified in this catalog Oct 16, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.