# CVE-2026-72279: KVM: arm64: nv: Respect read-only PFN when mapping L1 VNCR

> A flaw in Linux KVM arm64 nested virtualization allows guest writes to read-only memory, potentially enabling privilege escalation or data modification.

- **Severity:** Critical 9.0 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-72279, DEBIAN-CVE-2026-72279, GHSA-3627-jjwg-8vfw, UBUNTU-CVE-2026-72279

## What is CVE-2026-72279?

CVE-2026-72279 is a critical vulnerability in Linux, published on 15 Aug 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: arm64: nv: Respect read-only PFN when mapping L1 VNCR

KVM currently maps the L1 VNCR into the host stage-1 by relying entirely
on the permissions of the guest stage-1. At the same time, it is
entirely possible that the backing PFN is read-only (e.g. RO memslot),
meaning that the L1 VNCR should use at most a read-only mapping.

Cache the writability of the PFN in the VNCR TLB and use it to constrain
the resulting fixmap permissions. Promote VNCR permission faults to an
SEA in the case where the guest attempts to write to a read-only
endpoint. Conveniently, this also plugs a page leak found by Sashiko [*]
resulting from the early return for a read-only PFN.

## Which versions are affected by CVE-2026-72279?


## How do I fix CVE-2026-72279?

Apply the vendor's patch.

## Is CVE-2026-72279 being exploited?

There is no known exploitation of CVE-2026-72279 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72279 and fix it if it is affected.

What it is: CVE-2026-72279 is a critical vulnerability in Linux, published on 15 Aug 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-2026-72279 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-2026-72279/ (Markdown: https://insights.sbomify.com/CVE-2026-72279/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72279
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72279
- OSV: https://osv.dev/vulnerability/CVE-2026-72279

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72279/
Summaries are generated and may contain mistakes; the official description above is the record.