CVE-2026-97974

In the Linux kernel, the following vulnerability has been resolved: ipv6: null-check fib6_node before accessing in __ip6_del_rt_siblings() syzbot reported a null-ptr-deref in __ip6_del_rt_siblings() [0]. The stack trace hinted towards a null dereference of rt->fib6_node when fn->leaf is accessed in __ip6_del_rt_siblings(). With RTNL_FLAG_DOIT_UNLOCKED set, inet6_rtm_delroute() operations run concurrently without acquiring the RTNL lock. In ip6_route_del(), the route lookup happens under rcu_read_lock() without acquiring table->tb6_lock. Between ip6_route_del() looking up the route and __ip6_del_rt_siblings() acquiring table->tb6_lock, another thread can modify the routing table. For example, when an ECMP route is replaced via RTM_NEWROUTE with NLM_F_REPLACE, fib6_add_rt2node() unlinks all old siblings and sets iter->fib6_node = NULL. A reproducer was found that triggers this [1]. Add a check to ensure rt->fib6_node is non-null before accessing it. [0] KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027] RIP: 0010:__ip6_del_rt_siblings+0x31e/0x7c0 net/ipv6/route.c:4056 Call Trace: <TASK> ip6_route_del+0x1054/0x1110 net/ipv6/route.c:4232 inet6_rtm_delroute+0x5d7/0x6