# CVE-2026-89448: iommu/vt-d: Force requesting ACS when tboot is enabled

> Attackers may bypass IOMMU isolation when tboot is enabled if ACS is disabled, requiring a kernel patch to enforce correct configuration.

- **Severity:** Critical 9.3 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **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:** AZL-100874, BELL-CVE-2026-89448, DEBIAN-CVE-2026-89448, GHSA-mhhr-wjj6-vjmr, UBUNTU-CVE-2026-89448

## What is CVE-2026-89448?

CVE-2026-89448 is a critical 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/vt-d: Force requesting ACS when tboot is enabled

Currently the conditions of requesting ACS in detect_intel_iommu()
don't include tboot, leading to a possible misconfiguration with ACS
disabled (e.g. due to user opts) while iommu is later forced on by
tboot_force_iommu().

Fix it by checking tboot in detect_intel_iommu().

## Which versions are affected by CVE-2026-89448?


## How do I fix CVE-2026-89448?

Apply the vendor's patch.

## Is CVE-2026-89448 being exploited?

There is no known exploitation of CVE-2026-89448 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89448 and fix it if it is affected.

What it is: CVE-2026-89448 is a critical 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-2026-89448 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-2026-89448/ (Markdown: https://insights.sbomify.com/CVE-2026-89448/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89448
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89448
- OSV: https://osv.dev/vulnerability/CVE-2026-89448

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89448/
Summaries are generated and may contain mistakes; the official description above is the record.