# CVE-2026-89450: iommu/tegra241-cmdqv: Reject a vSID wider than the SID_MATCH field

> A guest VM can bypass IOMMU isolation by providing an oversized virtual Stream ID that aliases to a different device, potentially enabling privilege escalation.

- **Severity:** High 8.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-89450, DEBIAN-CVE-2026-89450, GHSA-4jcm-3g5m-55hr, UBUNTU-CVE-2026-89450

## What is CVE-2026-89450?

CVE-2026-89450 is a high-severity vulnerability in Linux, published on 11 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/tegra241-cmdqv: Reject a vSID wider than the SID_MATCH field

tegra241_vintf_init_vsid() programs the guest-provided vSID into SID_MATCH,
whose VIRT_SID field spans bits [20:1] with bit 0 as the match-enable flag.
The HW therefore matches only a 20-bit Stream ID.

The bound check rejects only virt_sid > UINT_MAX, which admits a value far
wider than the field. The write "virt_sid << 1 | 0x1" then drops every bit
above 20: a virt_sid of 0x80000000 lands as SID_MATCH = 0x1, a valid match
on vSID 0, so the entry aliases the wrong Stream ID. Because vdev->virt_id
is guest-controlled, a VMM can trigger it.

Validate virt_sid against the field width with FIELD_MAX(), and program the
register with FIELD_PREP() so the value and the field stay consistent.

## Which versions are affected by CVE-2026-89450?


## How do I fix CVE-2026-89450?

Apply the vendor's patch.

## Is CVE-2026-89450 being exploited?

There is no known exploitation of CVE-2026-89450 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89450 and fix it if it is affected.

What it is: CVE-2026-89450 is a high-severity vulnerability in Linux, published on 11 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-2026-89450 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-2026-89450/ (Markdown: https://insights.sbomify.com/CVE-2026-89450/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89450
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89450
- OSV: https://osv.dev/vulnerability/CVE-2026-89450

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89450/
Summaries are generated and may contain mistakes; the official description above is the record.