# CVE-2026-23558: grant table v2 race in status page mapping

> A race condition in Xen hypervisor allows guest VMs to trigger use-after-free, potentially leading to privilege escalation or code execution.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:H/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:** 19 May 2026
- **Updated:** 20 May 2026
- **Also known as:** ALPINE-CVE-2026-23558, DEBIAN-CVE-2026-23558, GHSA-4qf9-g5cf-cx9j, UBUNTU-CVE-2026-23558

## What is CVE-2026-23558?

CVE-2026-23558 is a high-severity vulnerability in Xen Xen, published on 19 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The adjustments made for XSA-379 as well as those subsequently becoming
XSA-387 still left a race window, when a HVM or PVH guest does a grant
table version change from v2 to v1 in parallel with mapping the status
page(s) via XENMEM_add_to_physmap.  Some of the status pages may then be
freed while mappings of them would still be inserted into the guest's
secondary (P2M) page tables.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2026-23558?

It affects 1 product.


Products: Xen Xen.

## How do I fix CVE-2026-23558?

Apply the vendor's patch.

## Is CVE-2026-23558 being exploited?

There is no known exploitation of CVE-2026-23558 in the wild and no public exploit code.

## Other vulnerabilities in Xen Xen

- [CVE-2017-10912](https://insights.sbomify.com/CVE-2017-10912/): Privilege escalation in n/a (critical 10.0)
- [CVE-2017-10918](https://insights.sbomify.com/CVE-2017-10918/): Memory corruption in n/a (critical 10.0)
- [CVE-2017-10920](https://insights.sbomify.com/CVE-2017-10920/): Memory corruption in n/a (critical 10.0)
- [CVE-2017-10921](https://insights.sbomify.com/CVE-2017-10921/): Memory corruption in n/a (critical 10.0)
- [CVE-2025-27466](https://insights.sbomify.com/CVE-2025-27466/): Mutiple vulnerabilities in the Viridian interface (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23558 and fix it if it is affected.

What it is: CVE-2026-23558 is a high-severity vulnerability in Xen Xen, published on 19 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-2026-23558 in the wild and no public exploit code.

Affected product: Xen Xen. 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-2026-23558/ (Markdown: https://insights.sbomify.com/CVE-2026-23558/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23558
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23558
- OSV: https://osv.dev/vulnerability/CVE-2026-23558

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23558/
Summaries are generated and may contain mistakes; the official description above is the record.