# CVE-2026-80817: iommu/iommufd: Fix NULL pointer deref in iommufd_ioas_change_process when racing with iopt_map_file_pages

> A race condition in the Linux kernel iommufd subsystem allows a local attacker to trigger a NULL pointer dereference, causing a system crash.

- **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:** 4 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-80817, DEBIAN-CVE-2026-80817, GHSA-wv8m-2pxf-rh83, UBUNTU-CVE-2026-80817

## What is CVE-2026-80817?

CVE-2026-80817 is a vulnerability in Linux, published on 4 Sep 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:

iommu/iommufd: Fix NULL pointer deref in iommufd_ioas_change_process when racing with iopt_map_file_pages

iommufd_ioas_change_process() iterates every IOAS area while only
holding every IOAS iova_rwsem, so it assumes every area has a non-NULL
pages pointer. That assumption can be false when it runs concurrently
with iopt_map_file_pages().

iopt_map_pages() executes in two phases. It first creates the area and
inserts it into the interval tree under iova_rwsem, with area->pages
still NULL. It then drops iova_rwsem and later fills area->pages
under domains_rwsem. This leaves a window between area creation and
area->pages fill where a concurrent iommufd_ioas_change_process()
can observe the area and dereference a NULL area->pages pointer,
leading to a NULL pointer dereference:

BUG: kernel NULL pointer dereference, address: 00000000000000c0
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 4b655067 P4D 4b655067 PUD 0
Oops: Oops: 0000 [#1] SMP NOPTI
CPU: 0 UID: 0 PID: 11841 Comm: syz.1.628 Not tainted 7.1.0 #3 PREEMPT(full)
Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:iommufd_ioas_change_process+0x419/0xd50 drivers/iommu/iommufd/ioas.c:538
Code: 48 89 c3 48 85 c0 0f 84 cc 00 00 00 e8 10 f5 cb fd 48 8d 7b 68 e8 a7 b5 eb fd 48 8b 6b 68 48 8d bd c0 00 00 00 e8 17 b2 eb fd <8b> ad c0 00 00 00 bf 01 00 00 00 89 ee e8 85 ef cb fd 83 fd 01 74
RSP: 0018:ffffc90015c17d28 EFLAGS: 00010246
RAX: ffff8880186d5328 RBX: ffff88801d25e240 RCX: 0000000080000000
RDX: 00000000000002d7 RSI: ffffffff83ba9e10 RDI: 00000000000000c0
RBP: 0000000000000000 R08: ffffffff8e781eb8 R09: 0000000000000000
R10: 00000000000000c0 R11: ffffffff83ba9e29 R12: ffff88802e216008
R13: ffff88802e216000 R14: 0000000000000001 R15: 0000000000000000
FS:  00007f4aea3f66c0(0000) GS:ffff8880b1fa1000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000000c0 CR3: 000000004b75c000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 iommufd_fops_ioctl+0x287/0x400 drivers/iommu/iommufd/main.c:533
 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+0x120/0x170 fs/ioctl.c:583
 x64_sys_call+0x1092/0x1fb0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10a/0x680 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4aec1a82bd
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:00007f4aea3f6018 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f4aec436090 RCX: 00007f4aec1a82bd
RDX: 0000200000000180 RSI: 0000000000003b92 RDI: 0000000000000003
RBP: 00007f4aec250295 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4aec436128 R14: 00007f4aec436090 R15: 00007ffd04ef23e0
 </TASK>
Modules linked in:
CR2: 00000000000000c0
---[ end trace 0000000000000000 ]---
RIP: 0010:iommufd_ioas_change_process+0x419/0xd50 drivers/iommu/iommufd/ioas.c:538
Code: 48 89 c3 48 85 c0 0f 84 cc 00 00 00 e8 10 f5 cb fd 48 8d 7b 68 e8 a7 b5 eb fd 48 8b 6b 68 48 8d bd c0 00 00 00 e8 17 b2 eb fd <8b> ad c0 00 00 00 bf 01 00 00 00 89 ee e8 85 ef cb fd 83 fd 01 74
RSP: 0018:ffffc90015c17d28 EFLAGS: 00010246
RAX: ffff8880186d5328 RBX: ffff88801d25e240 RCX: 0000000080000000
RDX: 00000000000002d7 RSI: ffffffff83ba9e10 RDI: 00000000000000c0
RBP: 0000000000000000 R08: ffffffff8e781eb8 R09: 0000000000000000
R10: 00000000000000c0 R11: ffffffff83ba9e29 R12: ffff88802e216008
R13: ffff88802e216000 R14: 0000000000000001 R15: 0000000000000000
FS:  00007f4aea3f66c0(000
---truncated---

## Which versions are affected by CVE-2026-80817?


## How do I fix CVE-2026-80817?

Apply the vendor's patch.

## Is CVE-2026-80817 being exploited?

There is no known exploitation of CVE-2026-80817 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80817 and fix it if it is affected.

What it is: CVE-2026-80817 is a vulnerability in Linux, published on 4 Sep 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-2026-80817 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-2026-80817/ (Markdown: https://insights.sbomify.com/CVE-2026-80817/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80817
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80817
- OSV: https://osv.dev/vulnerability/CVE-2026-80817

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80817/
Summaries are generated and may contain mistakes; the official description above is the record.