# CVE-2026-98508: drm/virtio: fix NULL pointer dereference on fence allocation failure

> A local attacker can cause a kernel crash in the virtio GPU driver by triggering a NULL pointer dereference during fence allocation failure.

- **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:** AZL-109157, BELL-CVE-2026-98508, DEBIAN-CVE-2026-98508, GHSA-4gjh-xj79-p5g5, UBUNTU-CVE-2026-98508

## What is CVE-2026-98508?

CVE-2026-98508 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/virtio: fix NULL pointer dereference on fence allocation failure

virtio_gpu_fence_alloc() can fail due to memory pressure and return NULL,
but its caller like virtio_gpu_init_submit() never checks it. Later,
virtio_gpu_init_submit() passes the NULL fence to
virtio_gpu_fence_event_create(), which unconditionally dereferences it.

Found when fuzzing the virtio driver with Syzkaller:

	Oops: general protection fault, probably for non-canonical address 0xdffffc0000000012: 0000 [#1] SMP KASAN NOPTI
	KASAN: null-ptr-deref in range [0x0000000000000090-0x0000000000000097]
	CPU: 1 UID: 0 PID: 9991 Comm: syz.0.121 Not tainted 7.2.0 #4 PREEMPT(full)
	Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014
	RIP: 0010:virtio_gpu_fence_event_create drivers/gpu/drm/virtio/virtgpu_submit.c:295 [inline]
	RIP: 0010:virtio_gpu_init_submit drivers/gpu/drm/virtio/virtgpu_submit.c:398 [inline]
	RIP: 0010:virtio_gpu_execbuffer_ioctl+0xc78/0x1aa0 drivers/gpu/drm/virtio/virtgpu_submit.c:505
	Code: 85 ed 0f 85 21 09 00 00 e8 05 5a c9 fb 48 8b 44 24 10 48 8d b8 90 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 9a 0d 00 00 48 8b 44 24 10 4c 89 b0 90 00 00 00
	RSP: 0018:ffffc900039dfad0 EFLAGS: 00010216
	RAX: dffffc0000000000 RBX: ffffc900039dfdd8 RCX: ffffffff85f6fd3d
	RDX: 0000000000000012 RSI: ffffffff85f6fd4b RDI: 0000000000000090
	RBP: 0000000000000000 R0virtio_gpu_virgl_process_cmd: ctrl 0x102, error 0x1203
	R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880132c4000
	R13: 0000000000000000 R14: ffff888073b6c700 R15: 000000000000003b
	FS:  00007fab480b96c0(0000) GS:ffff8880eb6e9000(0000) knlGS:0000000000000000
	CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
	CR2: 00007effbf5e55a8 CR3: 0000000048d19000 CR4: 0000000000350ef0
	Call Trace:
	<TASK>
	drm_ioctl_kernel+0x1f4/0x3e0 drivers/gpu/drm/drm_ioctl.c:817
	drm_ioctl+0x5f4/0xc70 drivers/gpu/drm/drm_ioctl.c:914
	vfs_ioctl fs/ioctl.c:51 [inline]
	__do_sys_ioctl fs/ioctl.c:597 [inline]
	__se_sys_ioctl fs/ioctl.c:583 [inline]
	__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
	do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
	do_syscall_64+0x116/0x800 arch/x86/entry/syscall_64.c:94
	entry_SYSCALL_64_after_hwframe+0x77/0x7f
	RIP: 0033:0x7fab471a82bd
	Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
	RSP: 002b:00007fab480b9018 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
	RAX: ffffffffffffffda RBX: 00007fab47435fa0 RCX: 00007fab471a82bd
	RDX: 00002000000000c0 RSI: 00000000c0406442 RDI: 0000000000000003
	RBP: 00007fab480b9080 R08: 0000000000000000 R09: 0000000000000000
	R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
	R13: 00007fab47436038 R14: 00007fab47435fa0 R15: 00007ffe85ab0740
	</TASK>
	Modules linked in:
	---[ end trace 0000000000000000 ]---
	RIP: 0010:virtio_gpu_fence_event_create drivers/gpu/drm/virtio/virtgpu_submit.c:295 [inline]
	RIP: 0010:virtio_gpu_init_submit drivers/gpu/drm/virtio/virtgpu_submit.c:398 [inline]
	RIP: 0010:virtio_gpu_execbuffer_ioctl+0xc78/0x1aa0 drivers/gpu/drm/virtio/virtgpu_submit.c:505
	Code: 85 ed 0f 85 21 09 00 00 e8 05 5a c9 fb 48 8b 44 24 10 48 8d b8 90 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 9a 0d 00 00 48 8b 44 24 10 4c 89 b0 90 00 00 00
	RSP: 0018:ffffc900039dfad0 EFLAGS: 00010216
	RAX: dffffc0000000000 RBX: ffffc900039dfdd8 RCX: ffffffff85f6fd3d
	RDX: 0000000000000012 RSI: ffffffff85f6fd4b RDI: 0000000000000090
	RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000
	R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880132c4000
	R13: 0000000000000000 R14: ffff888073b6c700 R15: 000000000000003b
	FS:  00007fab480b96c0(0000) GS:ffff888098ae9000(0000) knlGS:00000000
---truncated---

## Which versions are affected by CVE-2026-98508?


## How do I fix CVE-2026-98508?

Apply the vendor's patch.

## Is CVE-2026-98508 being exploited?

There is no known exploitation of CVE-2026-98508 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98508 and fix it if it is affected.

What it is: CVE-2026-98508 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-2026-98508 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-2026-98508/ (Markdown: https://insights.sbomify.com/CVE-2026-98508/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98508
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98508
- OSV: https://osv.dev/vulnerability/CVE-2026-98508

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98508/
Summaries are generated and may contain mistakes; the official description above is the record.