CVE-2026-74562

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

nexthop: take nh->lock for f6i_list walks in replace check and notify

fib6_check_nh_list() and __nexthop_replace_notify() walk nh->f6i_list

during an RTNL-serialized nexthop replace without holding nh->lock. IPv6

RTM_NEWROUTE/RTM_DELROUTE run without RTNL and mutate that list under

nh->lock (fib6_add_rt2node_nh(), fib6_purge_rt()), so both walks race a

concurrent route delete that unlinks and frees a fib6_info:

BUG: KASAN: slab-use-after-free in rt6_fill_node.isra.0 (net/ipv6/route.c:5799)

Read of size 4 at addr ffff888014607e64 by task exploit/143

rt6_fill_node.isra.0 (net/ipv6/route.c:5799)

fib6_rt_update (net/ipv6/route.c:6412)

__nexthop_replace_notify (net/ipv4/nexthop.c:2542)

rtm_new_nexthop (net/ipv4/nexthop.c:2554)

rtnetlink_rcv_msg (net/core/rtnetlink.c:7076)

BUG: KASAN: slab-use-after-free in fib6_check_nh_list (net/ipv4/nexthop.c:1605)

Read of size 8 at addr ffff888014a7d068 by task exploit/142

fib6_check_nh_list (net/ipv4/nexthop.c:1605)

rtm_new_nexthop (net/ipv4/nexthop.c:2575)

rtnetlink_rcv_msg (net/core/rtnetlink.c:7076)

Both walks only read the entries and take no tb6_lock, so protect them

with nh->lock; fib6_rt_update() uses gfp_any(), which returns GFP_ATOMIC

under the lock.