Linux Kernel: xfrm_nat_keepalive Work Rescheduling Race (CVE-2026-31406)
CVE-2026-31406 Published on April 6, 2026
xfrm: Fix work re-schedule after cancel in xfrm_nat_keepalive_net_fini()
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().
Products Associated with CVE-2026-31406
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Affected Versions
Linux:- Version f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae and below 32d0f44c2f14d60fe8e920e69a28c11051543ec1 is affected.
- Version f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae and below 2255ed6adbc3100d2c4a83abd9d0396d04b87792 is affected.
- Version f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae and below 21f2fc49ca6faa393c31da33b8a4e6c41fc84c13 is affected.
- Version f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae and below daf8e3b253aa760ff9e96c7768a464bc1d6b3c90 is affected.
- Version 6.11 is affected.
- Before 6.11 is unaffected.
- Version 6.12.80, <= 6.12.* is unaffected.
- Version 6.18.21, <= 6.18.* is unaffected.
- Version 6.19.11, <= 6.19.* is unaffected.
- Version 7.0-rc6, <= * is unaffected.