CVE-2026-99072

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

ipv4: stop route notification sizing when nexthop group shrinks

Commit 680aea08e78c ("net: ipv4: Emit notification when fib hardware flags are changed") added an RCU-only fib nlmsg size() call for asynchronous hardware flag notifications.

fib nlmsg size() checks fib info num path() before each iteration, then fib info nhc() independently reloads nh->nh grp. If RTM NEWNEXTHOP replaces a group with fewer paths between those loads, fib info nhc() returns NULL and fib nexthop nlmsg size() dereferences it.

Stop sizing when the indexed path is absent. Nexthop groups are dense, so the current snapshot has no later path.