CVE-2026-74496

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

fou: Fix use-after-free in fou_create()

fou_create() publishes struct fou through sk_user_data before adding the

new FOU port to the per-netns list. If fou_add_to_port_list() fails,

the error path frees fou while it is still reachable through

sk_user_data. A concurrent receive can then dereference the freed

object in fou_from_sock().

This ordering issue was previously noted in the linked discussion.

The failure is reachable when local port 0 is requested. Each socket

binds to a different ephemeral port, but fou_cfg_cmp() compares the

requested port 0 and reports -EALREADY once an entry already exists.

Release the tunnel socket before freeing fou so sk_user_data is cleared

first, and defer reclamation with kfree_rcu() to protect concurrent RCU

readers. This matches the lifetime handling in fou_release().