# CVE-2026-89908: LoongArch: KVM: Preserve memslot arch flags on KVM_MR_FLAGS_ONLY

> A flaw in Linux KVM for LoongArch allows guests to access wrong host pages due to lost memory slot flags, enabling unauthorized data access or modification.

- **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:** 16 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-89908, DEBIAN-CVE-2026-89908, GHSA-rfwm-m824-24pp, UBUNTU-CVE-2026-89908

## What is CVE-2026-89908?

CVE-2026-89908 is a high-severity memory corruption vulnerability in Linux, published on 16 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:

LoongArch: KVM: Preserve memslot arch flags on KVM_MR_FLAGS_ONLY

kvm_arch_prepare_memory_region() computes new->arch.flags, i.e. whether
a memslot is KVM_MEM_HUGEPAGE_CAPABLE or KVM_MEM_HUGEPAGE_INCAPABLE,
only for KVM_MR_CREATE and KVM_MR_MOVE, and returns early for every
other change. But the generic code allocates a zeroed memslot for every
change and never copies old->arch, so after a KVM_MR_FLAGS_ONLY update,
e.g. toggling KVM_MEM_LOG_DIRTY_PAGES for live migration, the active
memslot has arch.flags == 0.

With both flags clear, fault_supports_huge_mapping() falls through to
the alignment check on the HVA range alone, which no longer verifies
that the GPA and HVA have the same offset within a PMD. A memslot that
was marked KVM_MEM_HUGEPAGE_INCAPABLE because of a GPA/HVA offset
mismatch can then be mapped with PMD entries on read faults, and since
kvm_map_page() aligns the gfn and the pfn independently, the guest ends
up accessing the wrong host pages, exactly the "d -> f, e -> g" case
described in the comment above the check.

Carry the arch flags over from the old memslot for KVM_MR_FLAGS_ONLY,
as the GPA, HVA and size are guaranteed to be unchanged for that case.

## Which versions are affected by CVE-2026-89908?


## How do I fix CVE-2026-89908?

Apply the vendor's patch.

## Is CVE-2026-89908 being exploited?

There is no known exploitation of CVE-2026-89908 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89908 and fix it if it is affected.

What it is: CVE-2026-89908 is a high-severity memory corruption vulnerability in Linux, published on 16 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-2026-89908 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-2026-89908/ (Markdown: https://insights.sbomify.com/CVE-2026-89908/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89908
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89908
- OSV: https://osv.dev/vulnerability/CVE-2026-89908

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89908/
Summaries are generated and may contain mistakes; the official description above is the record.