# CVE-2026-98841: virt: vmgenid: set driver_data before registering notification handlers

> A race condition in the Linux kernel vmgenid driver causes a NULL pointer dereference and kernel panic when an interrupt fires before driver data is initialized.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **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:** BELL-CVE-2026-98841, DEBIAN-CVE-2026-98841, GHSA-p8pc-3hw3-fwp9, UBUNTU-CVE-2026-98841

## What is CVE-2026-98841?

CVE-2026-98841 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:

virt: vmgenid: set driver_data before registering notification handlers

Both probe paths register their notification handler before assigning
driver_data, which the handler dereferences.

In the devicetree path, the notification IRQ can fire as soon as
devm_request_irq() registers the handler: the interrupt may already be
pending at probe time, for example when a VMM injects the
generation-changed notification while restoring a guest from a snapshot
that was taken before the driver had probed (Firecracker does exactly
this on snapshot restore). The IRQ is also requested with IRQF_SHARED,
so another device sharing the line can trigger the handler just as
early. The handler then calls vmgenid_notify(), which dereferences the
still-NULL driver_data and panics:

  Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010
  CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.18.38+ #1 PREEMPT(none)
  Hardware name: linux,dummy-virt (DT)
  pc : vmgenid_notify.isra.0+0x24/0x8c
  lr : vmgenid_of_irq_handler+0x14/0x34
  Call trace:
   vmgenid_notify.isra.0+0x24/0x8c (P)
   vmgenid_of_irq_handler+0x14/0x34
   __handle_irq_event_percpu+0x44/0x1bc
   handle_irq_event+0x4c/0xb4
   handle_fasteoi_irq+0xf8/0x1f8

The ACPI path has the same ordering problem: the handler is installed
with acpi_install_notify_handler() before driver_data is assigned.
ACPI notifications are dispatched asynchronously from a workqueue, so
the window is narrow, but a notification arriving between the two calls
hits the same NULL dereference.

Assign driver_data before registering the handlers. The state is fully
initialized at that point, so the handlers are safe to run. Should
registration fail, the probe error path leaves no dangling pointer
behind: the driver core clears driver_data in device_unbind_cleanup().

## Which versions are affected by CVE-2026-98841?


## How do I fix CVE-2026-98841?

Apply the vendor's patch.

## Is CVE-2026-98841 being exploited?

There is no known exploitation of CVE-2026-98841 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98841 and fix it if it is affected.

What it is: CVE-2026-98841 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-2026-98841 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-2026-98841/ (Markdown: https://insights.sbomify.com/CVE-2026-98841/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98841
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98841
- OSV: https://osv.dev/vulnerability/CVE-2026-98841

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98841/
Summaries are generated and may contain mistakes; the official description above is the record.