# CVE-2026-98863: KVM: x86: Re-pend GET_NESTED_STATE_PAGES if getting said pages fails

> A flaw in Linux KVM allows local attackers to exploit stale page mappings, potentially leading to code execution or privilege escalation.

- **Severity:** Not scored
- **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:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-109449, BELL-CVE-2026-98863, DEBIAN-CVE-2026-98863, GHSA-8v5w-2f74-jcch, UBUNTU-CVE-2026-98863

## What is CVE-2026-98863?

CVE-2026-98863 is an use after free vulnerability in Linux, published on 18 Oct 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:

KVM: x86: Re-pend GET_NESTED_STATE_PAGES if getting said pages fails

Re-pend GET_NESTED_STATE_PAGES before exiting to userspace if getting the
nested pages fails in the KVM_RUN path.  If userspace re-runs the vCPU, and
vmcs02 holds valid PFNs from the *previous* run of L2, then KVM could
re-enter L2 with stale, unpinned PFNs mapped into e.g. the vAPIC page.

Note, both SVM and VMX (as of commit 11722439fb20 ("KVM: nVMX: Ensure
KVM_REQ_GET_NESTED_STATE_PAGES is cleared on VM-Exit") ensure the request
is cleared on VM-Exit (including the "forced" case), i.e. there is no risk
of double-mapping due to emulated VMLAUNCH/VMRESUME/VMRUN *and* the request
trying to map the nested pages.

## Which versions are affected by CVE-2026-98863?


## How do I fix CVE-2026-98863?

Apply the vendor's patch.

## Is CVE-2026-98863 being exploited?

There is no known exploitation of CVE-2026-98863 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98863 and fix it if it is affected.

What it is: CVE-2026-98863 is an use after free vulnerability in Linux, published on 18 Oct 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-2026-98863 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-2026-98863/ (Markdown: https://insights.sbomify.com/CVE-2026-98863/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98863
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98863
- OSV: https://osv.dev/vulnerability/CVE-2026-98863

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98863/
Summaries are generated and may contain mistakes; the official description above is the record.