CVE-2026-98787 bpf: Fix missing migration protection in __rhtab_map_lookup_and_delete_batch()
A race condition in the Linux kernel BPF subsystem can cause a kernel panic when deleting batch elements on preemptible RCU configurations.
- 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-2026-98787?
CVE-2026-98787 is a vulnerability in Linux, published on 18 Oct 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:
bpf: Fix missing migration protection in __rhtab_map_lookup_and_delete_batch()
bpf_mem_cache_free_rcu() uses this_cpu_ptr() which requires migration to be disabled. All callers of rhtab_delete_elem() disable migration except __rhtab_map_lookup_and_delete_batch(), which calls it under rcu_read_lock() only.
On CONFIG_PREEMPT_RCU, rcu_read_lock() does not disable preemption or migration, so the task can migrate between CPUs during the delete loop, causing this_cpu_ptr() to trigger:
BUG: using smp_processor_id() in preemptible [00000000] code
Fix by wrapping the delete loop in migrate_disable()/migrate_enable() in __rhtab_map_lookup_and_delete_batch(), matching the migration protection that the other callers already provide.
Which versions are affected by CVE-2026-98787?
How do I fix CVE-2026-98787?
Apply the vendor's patch.
Is CVE-2026-98787 being exploited?
There is no known exploitation of CVE-2026-98787 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-98787, GHSA-c3cw-2pj9-44qj, UBUNTU-CVE-2026-98787.