# CVE-2026-62430: x86: Out-of-bounds read in vRTC emulation

> A race condition in Xen's vRTC emulation allows a guest to trigger an out-of-bounds read, potentially disclosing host memory contents.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **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-2026-62430, DEBIAN-CVE-2026-62430, GHSA-w4qm-qcx6-wmw8, UBUNTU-CVE-2026-62430

## What is CVE-2026-62430?

CVE-2026-62430 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

Accesses to the CMOS memory contents are done using an indirect IO port
pair.  Therefore Xen needs to cache the guest chosen index, and one of
the usages of the index didn't take the necessary locking to avoid
concurrent changes.  As a result, a guest could change the index after
it being checked, causing a subsequent out-of-bound read access to the
contents of an array.

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

## Which versions are affected by CVE-2026-62430?


## How do I fix CVE-2026-62430?

Apply the vendor's patch.

## Is CVE-2026-62430 being exploited?

There is no known exploitation of CVE-2026-62430 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-62430 and fix it if it is affected.

What it is: CVE-2026-62430 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-2026-62430 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-2026-62430/ (Markdown: https://insights.sbomify.com/CVE-2026-62430/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-62430
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-62430
- OSV: https://osv.dev/vulnerability/CVE-2026-62430

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-62430/
Summaries are generated and may contain mistakes; the official description above is the record.