# CVE-2026-43253: iommu/amd: move wait_on_sem() out of spinlock

> A Linux kernel bug causes soft lockups during IOMMU operations when strict mode is enabled, leading to system unavailability.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 May 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-43253, DEBIAN-CVE-2026-43253, GHSA-jqx2-5f2v-644h, ROOT-OS-DEBIAN-11-CVE-2026-43253, ROOT-OS-DEBIAN-12-CVE-2026-43253, ROOT-OS-UBUNTU-2204-CVE-2026-43253, ROOT-OS-UBUNTU-2404-CVE-2026-43253, UBUNTU-CVE-2026-43253

## What is CVE-2026-43253?

CVE-2026-43253 is a high-severity denial of service vulnerability in Linux kernel, published on 6 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

iommu/amd: move wait_on_sem() out of spinlock

With iommu.strict=1, the existing completion wait path can cause soft
lockups under stressed environment, as wait_on_sem() busy-waits under the
spinlock with interrupts disabled.

Move the completion wait in iommu_completion_wait() out of the spinlock.
wait_on_sem() only polls the hardware-updated cmd_sem and does not require
iommu->lock, so holding the lock during the busy wait unnecessarily
increases contention and extends the time with interrupts disabled.

Weakness: CWE-667 (Improper Locking), CWE-833 (Deadlock)

## Which versions are affected by CVE-2026-43253?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43253?

Apply the vendor's patch.

## Is CVE-2026-43253 being exploited?

There is no known exploitation of CVE-2026-43253 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-2026-43253 and fix it if it is affected.

What it is: CVE-2026-43253 is a high-severity denial of service vulnerability in Linux kernel, published on 6 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-43253 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-2026-43253/ (Markdown: https://insights.sbomify.com/CVE-2026-43253/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43253
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43253
- OSV: https://osv.dev/vulnerability/CVE-2026-43253

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43253/
Summaries are generated and may contain mistakes; the official description above is the record.