# CVE-2023-34328: x86/AMD: Debug Mask handling

> A malicious PV guest can lock up the CPU by placing a breakpoint over the live GDT, causing a denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 5 Jan 2024
- **Updated:** 4 Nov 2025
- **Also known as:** ALPINE-CVE-2023-34328, DEBIAN-CVE-2023-34328, GHSA-fm4g-p248-j5wj, UBUNTU-CVE-2023-34328

## What is CVE-2023-34328?

CVE-2023-34328 is a medium-severity denial of service vulnerability in Xen Xen, published on 5 Jan 2024. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

[This CNA information record relates to multiple CVEs; the
text explains which aspects/vulnerabilities correspond to which CVE.]

AMD CPUs since ~2014 have extensions to normal x86 debugging functionality.
Xen supports guests using these extensions.

Unfortunately there are errors in Xen's handling of the guest state, leading
to denials of service.

 1) CVE-2023-34327 - An HVM vCPU can end up operating in the context of
    a previous vCPUs debug mask state.

 2) CVE-2023-34328 - A PV vCPU can place a breakpoint over the live GDT.
    This allows the PV vCPU to exploit XSA-156 / CVE-2015-8104 and lock
    up the CPU entirely.

## Which versions are affected by CVE-2023-34328?

It affects 1 product.


Products: Xen Xen.

## How do I fix CVE-2023-34328?

Apply the vendor's patch.

## Is CVE-2023-34328 being exploited?

There is no known exploitation of CVE-2023-34328 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-2023-34328 and fix it if it is affected.

What it is: CVE-2023-34328 is a medium-severity denial of service vulnerability in Xen Xen, published on 5 Jan 2024. 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-2023-34328 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-2023-34328/ (Markdown: https://insights.sbomify.com/CVE-2023-34328/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-34328
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-34328
- OSV: https://osv.dev/vulnerability/CVE-2023-34328

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-34328/
Summaries are generated and may contain mistakes; the official description above is the record.