# 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.

- **Severity:** Not scored
- **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:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-98787, GHSA-c3cw-2pj9-44qj, UBUNTU-CVE-2026-98787

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98787 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-98787 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98787/ (Markdown: https://insights.sbomify.com/CVE-2026-98787/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98787
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98787
- OSV: https://osv.dev/vulnerability/CVE-2026-98787

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98787/
Summaries are generated and may contain mistakes; the official description above is the record.