CVE-2026-64576nexthop: initialize extack in nh_res_bucket_migrate()

Official description

In the Linux kernel, the following vulnerability has been resolved: nexthop: initialize extack in nh_res_bucket_migrate() nh_res_bucket_migrate() passes an uninitialized netlink_ext_ack to call_nexthop_res_bucket_notifiers(). When nh_notifier_res_bucket_info_init() 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 pr_err_ratelimited("%s\n", extack._msg). With CONFIG_INIT_STACK_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) nh_res_bucket_migrate (net/ipv4/nexthop.c:1816) nh_res_table_upkeep (net/ipv4/nexthop.c:1866) rtm_new_nexthop (net/ipv4/nexthop.c:3323) rtnetlink_rcv_msg (net/core/rtnetlink.c:7076) netlink_sendmsg (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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/eacd2e2117e8682f937967fda1022e7f1c22d91a
• https://git.kernel.org/stable/c/37bbd7e1d8df0bec3d187e961783e20c30533d2c
• https://git.kernel.org/stable/c/c0936c131a71657afc635d0db2ab096d15d473e1
• https://git.kernel.org/stable/c/3081702ea5aca0aeed9c1ade8eadf6cde8db6b7d
• https://git.kernel.org/stable/c/d536bf205c71f700f6de2086038c3e1d77724715
• https://git.kernel.org/stable/c/18506d7263768d76ac8e057ba55a4d9da50aad66
• https://git.kernel.org/stable/c/6347c5314cee49f364aaf2e40ff15415a57a116e