# CVE-2026-31735: iommupt: Fix short gather if the unmap goes into a large mapping

> A logic error in the Linux kernel IOMMU unmap path could cause incomplete TLB invalidation, though it is likely not triggerable in practice.

- **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:** 1 May 2026
- **Updated:** 5 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-31735, GHSA-3h92-2gxm-w9x7, UBUNTU-CVE-2026-31735

## What is CVE-2026-31735?

CVE-2026-31735 is a high-severity vulnerability in Linux kernel, published on 1 May 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:

iommupt: Fix short gather if the unmap goes into a large mapping

unmap has the odd behavior that it can unmap more than requested if the
ending point lands within the middle of a large or contiguous IOPTE.

In this case the gather should flush everything unmapped which can be
larger than what was requested to be unmapped. The gather was only
flushing the range requested to be unmapped, not extending to the extra
range, resulting in a short invalidation if the caller hits this special
condition.

This was found by the new invalidation/gather test I am adding in
preparation for ARMv8. Claude deduced the root cause.

As far as I remember nothing relies on unmapping a large entry, so this is
likely not a triggerable bug.

## Which versions are affected by CVE-2026-31735?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31735?

Apply the vendor's patch.

## Is CVE-2026-31735 being exploited?

There is no known exploitation of CVE-2026-31735 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-2026-31735 and fix it if it is affected.

What it is: CVE-2026-31735 is a high-severity vulnerability in Linux kernel, published on 1 May 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-2026-31735 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-2026-31735/ (Markdown: https://insights.sbomify.com/CVE-2026-31735/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31735
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31735
- OSV: https://osv.dev/vulnerability/CVE-2026-31735

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31735/
Summaries are generated and may contain mistakes; the official description above is the record.