# CVE-2026-53283: iommu/amd: Bounds-check devid in __rlookup_amd_iommu()

> A missing bounds check in the AMD IOMMU driver causes a general protection fault and system crash during boot on specific virtualized hardware.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **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:** 26 Jun 2026
- **Updated:** 26 Jun 2026
- **Also known as:** BELL-CVE-2026-53283, DEBIAN-CVE-2026-53283, GHSA-gv9j-3945-3x3r, UBUNTU-CVE-2026-53283

## What is CVE-2026-53283?

CVE-2026-53283 is a medium-severity vulnerability in Linux kernel, published on 26 Jun 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/amd: Bounds-check devid in __rlookup_amd_iommu()

iommu_device_register() walks every device on the PCI bus via
bus_for_each_dev() and calls amd_iommu_probe_device() for each. The
inlined check_device() path computes the device's sbdf, calls
rlookup_amd_iommu() to find the owning IOMMU, and only afterwards
verifies devid <= pci_seg->last_bdf. __rlookup_amd_iommu() indexes
rlookup_table[devid] with no bounds check of its own, so for a PCI
device whose BDF is not described by the IVRS, the lookup reads past
the end of the allocation before the caller's bounds check can run.

This was harmless before commit e874c666b15b ("iommu/amd: Change
rlookup, irq_lookup, and alias to use kvalloc()"): the table was a
zeroed page-order allocation, so the over-read returned NULL and the
caller's NULL check skipped the device. After that commit the table is
a tight kvcalloc() and the over-read returns adjacent slab contents,
which check_device() then dereferences as a struct amd_iommu *,
causing a boot-time GPF.

Seen on Google Compute Engine ct6e VMs, where the virtualized IVRS
describes only the four TPU endpoints 00:04.0-07.0; the gVNIC at
00:08.0 (devid 0x40) indexes 56 bytes past the 456-byte allocation,
into the adjacent kmalloc-512 slab object:

  pci 0000:00:04.0: Adding to iommu group 0
  pci 0000:00:05.0: Adding to iommu group 1
  pci 0000:00:06.0: Adding to iommu group 2
  pci 0000:00:07.0: Adding to iommu group 3
  Oops: general protection fault, probably for non-canonical address 0x3a64695f78746382: 0000 [#1] SMP NOPTI
  CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.18.22 #1
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/06/2025
  RIP: 0010:amd_iommu_probe_device+0x54/0x3a0
  Call Trace:
   __iommu_probe_device+0x107/0x520
   probe_iommu_group+0x29/0x50
   bus_for_each_dev+0x7e/0xe0
   iommu_device_register+0xc9/0x240
   iommu_go_to_state+0x9c0/0x1c60
   amd_iommu_init+0x14/0x40
   pci_iommu_init+0x16/0x60
   do_one_initcall+0x47/0x2f0

Guard the array access in __rlookup_amd_iommu(). With the fix applied
on 6.18.22, the gVNIC at 00:08.0 is skipped cleanly and the VM boots.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-53283?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53283?

Apply the vendor's patch.

## Is CVE-2026-53283 being exploited?

There is no known exploitation of CVE-2026-53283 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53283 and fix it if it is affected.

What it is: CVE-2026-53283 is a medium-severity vulnerability in Linux kernel, published on 26 Jun 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-2026-53283 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-53283/ (Markdown: https://insights.sbomify.com/CVE-2026-53283/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53283
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53283
- OSV: https://osv.dev/vulnerability/CVE-2026-53283

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53283/
Summaries are generated and may contain mistakes; the official description above is the record.