CVE-2026-31406

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

xfrm: Fix work re-schedule after cancel in xfrm_nat_keepalive_net_fini()

After cancel_delayed_work_sync() is called from xfrm_nat_keepalive_net_fini(), xfrm_state_fini() flushes remaining states via __xfrm_state_delete(), which calls xfrm_nat_keepalive_state_updated() to re-schedule nat_keepalive_work.

The following is a simple race scenario:

       cpu0                             cpu1

cleanup_net() [Round 1] ops_undo_list() xfrm_net_exit() xfrm_nat_keepalive_net_fini() cancel_delayed_work_sync(nat_keepalive_work); xfrm_state_fini() xfrm_state_flush() xfrm_state_delete(x) __xfrm_state_delete(x) xfrm_nat_keepalive_state_updated(x) schedule_delayed_work(nat_keepalive_work); rcu_barrier(); net_complete_free(); net_passive_dec(net); llist_add(&net->defer_free_list, &defer_free_list);

cleanup_net() [Round 2] rcu_barrier(); net_complete_free() kmem_cache_free(net_cachep, net); nat_keepalive_work() // on freed net

To prevent this, cancel_delayed_work_sync() is replaced with disable_delayed_work_sync().

Affected Software

References

• https://git.kernel.org/stable/c/21f2fc49ca6faa393c31da33b8a4e6c41fc84c13
• https://git.kernel.org/stable/c/2255ed6adbc3100d2c4a83abd9d0396d04b87792
• https://git.kernel.org/stable/c/32d0f44c2f14d60fe8e920e69a28c11051543ec1
• https://git.kernel.org/stable/c/daf8e3b253aa760ff9e96c7768a464bc1d6b3c90