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.
- 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-2026-98523?
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.
Sources
Also known as BELL-CVE-2026-98523, DEBIAN-CVE-2026-98523, GHSA-hc5h-vrq3-w82j, UBUNTU-CVE-2026-98523.