# CVE-2026-42492: vIRQ event channel binding may break Xenstore

> Unprivileged domains can trigger an error path that tears down an uninitialized bitmap, breaking Xenstore and causing denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Jul 2026
- **Updated:** 28 Jul 2026
- **Also known as:** ALPINE-CVE-2026-42492, GHSA-2hv5-3qjg-gjqr, UBUNTU-CVE-2026-42492

## What is CVE-2026-42492?

CVE-2026-42492 is a high-severity vulnerability in Xen, published on 28 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Xenstore, to have an up-to-date picture of the entire system, wants to
know of domains appearing and disappearing.  To make this more robust, a
new XEN_DOMCTL_get_domain_state was introduced.  The management of the
bitmap underlying that operation is tied into the binding of the
VIRQ_DOM_EXC virtual IRQ.  Unfortunately an error path there would tear
down the bitmap even in cases when it wasn't set up.  Unprivileged domains
can trigger that error path.

Weakness: CWE-459 (Incomplete Cleanup)

## Which versions are affected by CVE-2026-42492?


## How do I fix CVE-2026-42492?

Apply the vendor's patch.

## Is CVE-2026-42492 being exploited?

There is no known exploitation of CVE-2026-42492 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42492 and fix it if it is affected.

What it is: CVE-2026-42492 is a high-severity vulnerability in Xen, published on 28 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-42492 in the wild and no public exploit code.

Affected product: 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-2026-42492/ (Markdown: https://insights.sbomify.com/CVE-2026-42492/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42492
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42492
- OSV: https://osv.dev/vulnerability/CVE-2026-42492

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42492/
Summaries are generated and may contain mistakes; the official description above is the record.