# CVE-2020-15563: Null dereference in n/a

> A malicious x86 HVM guest can crash the Xen hypervisor via a null pointer dereference in video RAM tracking, causing host-wide denial of service.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/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:** 7 Jul 2020
- **Updated:** 4 Aug 2024
- **Also known as:** ALPINE-CVE-2020-15563, DEBIAN-CVE-2020-15563, GHSA-wwfw-7rgm-hmmc, UBUNTU-CVE-2020-15563

## What is CVE-2020-15563?

CVE-2020-15563 is a medium-severity vulnerability in Debian Debian Linux, published on 7 Jul 2020. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An issue was discovered in Xen through 4.13.x, allowing x86 HVM guest OS users to cause a hypervisor crash. An inverted conditional in x86 HVM guests' dirty video RAM tracking code allows such guests to make Xen de-reference a pointer guaranteed to point at unmapped space. A malicious or buggy HVM guest may cause the hypervisor to crash, resulting in Denial of Service (DoS) affecting the entire host. Xen versions from 4.8 onwards are affected. Xen versions 4.7 and earlier are not affected. Only x86 systems are affected. Arm systems are not affected. Only x86 HVM guests using shadow paging can leverage the vulnerability. In addition, there needs to be an entity actively monitoring a guest's video frame buffer (typically for display purposes) in order for such a guest to be able to leverage the vulnerability. x86 PV guests, as well as x86 HVM guests using hardware assisted paging (HAP), cannot leverage the vulnerability.

Weakness: CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2020-15563?

It affects 4 products.


Products: Debian Debian Linux, Fedoraproject Fedora, Opensuse Leap, Xen Xen.

## How do I fix CVE-2020-15563?

Apply the vendor's patch.

## Is CVE-2020-15563 being exploited?

There is no known exploitation of CVE-2020-15563 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

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- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-15563 and fix it if it is affected.

What it is: CVE-2020-15563 is a medium-severity vulnerability in Debian Debian Linux, published on 7 Jul 2020. 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-2020-15563 in the wild and no public exploit code.

Affected product: Debian Debian 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-2020-15563/ (Markdown: https://insights.sbomify.com/CVE-2020-15563/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-15563
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-15563
- OSV: https://osv.dev/vulnerability/CVE-2020-15563

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-15563/
Summaries are generated and may contain mistakes; the official description above is the record.