CVE-2026-64123 net: hsr: defer node table free until after RCU readers
A use-after-free in the Linux kernel HSR module allows attackers to cause denial of service or execute code via race conditions during node table deletion.
- 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-2026-64123?
CVE-2026-64123 is a high-severity use after free vulnerability in Linux kernel, published on 19 Jul 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:
net: hsr: defer node table free until after RCU readers
HSR node-list and node-status generic-netlink operations run under rcu_read_lock(). They walk hsr->node_db through hsr_get_next_node() and hsr_get_node_data(), but RTM_DELLINK teardown removes the same node table with plain list_del() and frees each node immediately.
That lets a generic-netlink reader hold a struct hsr_node pointer across hsr_dellink(). In a KASAN build, widening the reader window after hsr_get_next_node() obtains the node reproduces a slab-use-after-free when the reader copies node->macaddress_A; the freeing stack is hsr_del_nodes() from hsr_dellink().
Use list_del_rcu() and defer the free through the existing hsr_free_node_rcu() callback. This matches the lifetime rule used by the HSR prune paths, which already delete nodes with list_del_rcu() and call_rcu().
Weakness: CWE-416
Which versions are affected by CVE-2026-64123?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64123?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-64123 being exploited?
There is no known exploitation of CVE-2026-64123 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-64123, DEBIAN-CVE-2026-64123, GHSA-q3v2-68cr-qhrm, ROOT-OS-UBUNTU-2204-CVE-2026-64123, UBUNTU-CVE-2026-64123.