CVE-2026-64576 nexthop: initialize extack in nh_res_bucket_migrate()
An uninitialized pointer dereference in the Linux kernel nexthop module can cause a kernel panic, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64576?
CVE-2026-64576 is a high-severity vulnerability in Linux, published on 5 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
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.
Weakness: CWE-457
Which versions are affected by CVE-2026-64576?
How do I fix CVE-2026-64576?
Apply the vendor's patch.
Is CVE-2026-64576 being exploited?
There is no known exploitation of CVE-2026-64576 in the wild and no public exploit code.
Sources
Also known as AZL-94461, BELL-CVE-2026-64576, DEBIAN-CVE-2026-64576, GHSA-pg7w-xrhc-whgh, UBUNTU-CVE-2026-64576.