# CVE-2026-98523: drm/client: fix restore of partially initialized client

> A local attacker can trigger a kernel NULL pointer dereference and crash the system by closing a DRM file descriptor after a failed client initialization.

- **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:** BELL-CVE-2026-98523, DEBIAN-CVE-2026-98523, GHSA-hc5h-vrq3-w82j, UBUNTU-CVE-2026-98523

## What is CVE-2026-98523?

CVE-2026-98523 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:

drm/client: fix restore of partially initialized client

I got a null-ptr-deref report when closing a DRM file descriptor:

WARNING: drivers/gpu/drm/drm_atomic.c:2031 at
__drm_atomic_helper_set_config+0x18e/0x1b0 [drm]

Call Trace:
drm_client_modeset_commit_atomic+0x16b/0x220 [drm]
drm_client_modeset_commit_locked+0x56/0x160 [drm]
drm_client_modeset_commit+0x21/0x40 [drm]
__drm_fb_helper_restore_fbdev_mode_unlocked.part.0+0x7b/0x80
drm_fbdev_client_restore+0xe/0x20 [drm_client_lib]
drm_client_dev_restore+0x9f/0xc0 [drm]
drm_release+0xc5/0xe0 [drm]

The warning is followed by a NULL pointer dereference:

BUG: kernel NULL pointer dereference, address: 0000000000000008

RIP:
__drm_fb_helper_restore_fbdev_mode_unlocked.part.0+0x41/0x80
[drm_kms_helper]

Call Trace:
drm_fbdev_client_restore+0xe/0x20 [drm_client_lib]
drm_client_dev_restore+0x9f/0xc0 [drm]
drm_release+0xc5/0xe0 [drm]
__fput+0xdc/0x2b0
__x64_sys_close+0x39/0x80
do_syscall_64+0x8d/0x460
entry_SYSCALL_64_after_hwframe+0x76/0x7e

drm_client_register() adds the DRM client to the device client list
before invoking the initial hotplug callback. If the hotplug callback
fails, the client remains registered.

For the fbdev client, a failure during drm_fb_helper_initial_config()
causes the partially initialized fbdev helper to be cleaned up.
drm_fb_helper_fini() releases fb_helper->info and leaves it NULL.

The fbdev client therefore remains registered even though there is no
fully initialized framebuffer device.

Later, when userspace closes the DRM file descriptor, drm_release()
can invoke the restore callbacks of registered DRM clients:

drm_release()
drm_client_dev_restore()
drm_fbdev_client_restore()
drm_fb_helper_restore_fbdev_mode_unlocked()

drm_fbdev_client_restore() currently restores the fbdev state
unconditionally. For a partially initialized fbdev client this can
submit an incomplete modeset state and subsequently access fbdev
state which has not been initialized, resulting in the warning and
NULL pointer dereference above.

drm_fbdev_client_unregister() already uses fb_helper->info to
distinguish a fully probed framebuffer device from a partially
initialized client.

Use the same condition in drm_fbdev_client_restore() and skip restore
if no framebuffer device has been successfully initialized.

## Which versions are affected by CVE-2026-98523?


## How do I fix CVE-2026-98523?

Apply the vendor's patch.

## Is CVE-2026-98523 being exploited?

There is no known exploitation of CVE-2026-98523 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98523 and fix it if it is affected.

What it is: CVE-2026-98523 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-2026-98523 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-2026-98523/ (Markdown: https://insights.sbomify.com/CVE-2026-98523/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98523
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98523
- OSV: https://osv.dev/vulnerability/CVE-2026-98523

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98523/
Summaries are generated and may contain mistakes; the official description above is the record.