LiveActive security incident?Get immediate response
CVE Record

CVE-2025-39925: can: j1939: implement NETDEV_UNREGISTER notification handler

In the Linux kernel, the following vulnerability has been resolved: can: j1939: implement NETDEV_UNREGISTER notification handler syzbot is reporting unregister_netdevice: waiting for vcan0 to become free. Usage count = 2 problem, for j1939 protocol did not have NETDEV_UNREGISTER notification handler for undoing changes made by j1939_sk_bind(). Commit 25fe97cb7620 ("can: j1939: move j1939_priv_put() into sk_destruct callback") expects that a call to j1939_priv_put() can be unconditionally delayed until j1939_sk_sock_destruct() is called. But we need to call j1939_priv_put() against an extra ref held by j1939_sk_bind() call (as a part of undoing changes made by j1939_sk_bind()) as soon as NETDEV_UNREGISTER notification fires (i.e. before j1939_sk_sock_destruct() is called via j1939_sk_release()). Otherwise, the extra ref on "struct j1939_priv" held by j1939_sk_bind() call prevents "struct net_device" from dropping the usage count to 1; making it impossible for unregister_netdevice() to continue. [mkl: remove space in front of label]

MediumCVSS 5.5Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2025-39925 is a Linux kernel availability issue in the CAN J1939 networking code. A local user with privileges can trigger a device-unregister path that fails to release a reference, leaving the kernel waiting and potentially causing denial of service. No public source here shows active exploitation.

Executive priority

Treat this as a moderate-priority availability risk. It is not shown as actively exploited, but local denial-of-service bugs in kernels can matter on shared, industrial, embedded, or containerized Linux systems where CAN networking is available.

Technical view

The J1939 protocol lacked a NETDEV_UNREGISTER notification handler to undo state from j1939_sk_bind(). An extra j1939_priv reference could keep struct net_device usage elevated, preventing unregister_netdevice() from completing. The CVSS vector is local, low complexity, low privilege, no user interaction, availability impact only.

Likely exposure

Exposure is most likely on Linux systems where CAN J1939 support is enabled or loadable and local users can interact with relevant networking capabilities. The source lists Linux kernel versions including 5.4, 6.16.8, and 6.17 as affected; distro backports may change practical exposure.

Exploitation context

The provided sources do not show KEV listing or active exploitation. The issue was reported by syzbot and requires local access with privileges. Impact is denial of service, not confidentiality or integrity compromise, based on the supplied CVSS vector.

Researcher notes

The fix implements NETDEV_UNREGISTER handling so bind-time J1939 private references are released before socket destruction. Evidence is limited to the CVE record and upstream stable commit references; no exploitability details beyond CVSS and syzbot-triggered behavior are provided.

Mitigation direction

  • Check Linux distribution advisories for fixed kernel packages.
  • Update to a kernel containing the referenced stable fixes.
  • Prioritize systems exposing CAN/J1939 to local users or containers.
  • Limit unnecessary local access to CAN networking capabilities.
  • Track vendor backports rather than relying only on upstream version numbers.

Validation and detection

  • Inventory running kernel versions across Linux hosts.
  • Confirm whether CAN J1939 support is enabled, loadable, or used.
  • Compare vendor kernel changelogs against the referenced stable commits.
  • Review logs for unregister_netdevice waiting messages on CAN devices.
  • Validate remediation in staging before broad kernel rollout.
Prepared
Confidence
high
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cve · low confidence lookup

CVE-2025-39925 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
1ADP providers
3Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
5.5CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H1.83.6CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

5.5Medium
CVSS 3.1 vector shape for CVE-2025-39925Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux9d71dd0c70099914fcd063135da3c580865e924c, 9d71dd0c70099914fcd063135da3c580865e924cunaffected
LinuxLinux5.4, 0, 6.16.8, 6.17affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.