CVE-2025-71182: can: j1939: make j1939_session_activate() fail if device is no longer registered

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-01-31 · updated 2026-10-19
Weakness: CWE-362

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.

Affected products

Linux kernel: from 5.4.1 before 5.10.248; from 5.11 before 5.15.198; from 5.16 before 6.1.161; from 6.2 before 6.6.121; from 6.7 before 6.12.66; from 6.13 before 6.18.6 — fixed in 5.10.248, 5.15.198, 6.1.161, 6.12.66, 6.18.6, 6.6.121

How to fix

Upgrade to a fixed version: Linux kernel 5.10.248, 5.15.198, 6.1.161, 6.12.66. Check the vendor advisory for mitigations.

References

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