CVE-2026-64576

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

nexthop: initialize extack in nhresbucket_migrate()

nhresbucketmigrate() passes an uninitialized netlinkextack to callnexthopresbucketnotifiers(). When nhnotifierresbucketinfoinit() fails (e.g. the kzalloc returns -ENOMEM), the error is propagated back before any notifier sets extack.msg, and the error path formats the stale pointer with prerrratelimited("%s\n", extack.msg). With CONFIGINITSTACK_NONE this dereferences uninitialized stack memory:

Oops: general protection fault, probably for non-canonical address ... KASAN: maybe wild-memory-access in range [...] RIP: 0010:string (lib/vsprintf.c:730) vsnprintf (lib/vsprintf.c:2945) printk (kernel/printk/printk.c:2504) nhresbucketmigrate (net/ipv4/nexthop.c:1816) nhrestableupkeep (net/ipv4/nexthop.c:1866) rtmnewnexthop (net/ipv4/nexthop.c:3323) rtnetlinkrcvmsg (net/core/rtnetlink.c:7076) netlinksendmsg (net/netlink/af_netlink.c:1900) Kernel panic - not syncing: Fatal exception

Zero-initialize extack so _msg is NULL on error paths that never set it.