# CVE-2026-89568: kho: fix size calculation in kho_preserved_memory_reserve()

> A local attacker with high privileges can trigger undefined behavior and potential denial of service by requesting memory reservations larger than 2 GiB due to an integer overflow in size calculation.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **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-2026-89568, DEBIAN-CVE-2026-89568, GHSA-832m-273v-9hpc, UBUNTU-CVE-2026-89568

## What is CVE-2026-89568?

CVE-2026-89568 is a 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:

kho: fix size calculation in kho_preserved_memory_reserve()

kho_preserved_memory_reserve() calculates the size of a preservation by
doing 1 << (order + PAGE_SHIFT). Since the '1' is a 32-bit integer, it
can only be shifted by 31. That is, it will only work for preservations
up to 2 GiB. Larger preservations will trigger undefined behaviour.

While preservations larger than 2 GiB can't be obtained via folios
currently, they can be obtained via kho_preserve_pages().

For example, memblock reserve_mem uses kho_preserve_pages().
Reservations larger than 2 GiB are valid and will trigger this bug if
properly aligned.

Fix it by using 1UL for shifting.

## Which versions are affected by CVE-2026-89568?


## How do I fix CVE-2026-89568?

Apply the vendor's patch.

## Is CVE-2026-89568 being exploited?

There is no known exploitation of CVE-2026-89568 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89568 and fix it if it is affected.

What it is: CVE-2026-89568 is a 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-2026-89568 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-2026-89568/ (Markdown: https://insights.sbomify.com/CVE-2026-89568/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89568
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89568
- OSV: https://osv.dev/vulnerability/CVE-2026-89568

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89568/
Summaries are generated and may contain mistakes; the official description above is the record.