# CVE-2020-25596: Denial of service in n/a

> Malicious userspace in x86 PV guests can crash the guest kernel via SYSENTER, causing VM 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:** 23 Sep 2020
- **Updated:** 4 Aug 2024
- **Also known as:** ALPINE-CVE-2020-25596, DEBIAN-CVE-2020-25596, GHSA-wv5g-6p8m-2pxx, UBUNTU-CVE-2020-25596

## What is CVE-2020-25596?

CVE-2020-25596 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 23 Sep 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 4.14.x. x86 PV guest kernels can experience denial of service via SYSENTER. The SYSENTER instruction leaves various state sanitization activities to software. One of Xen's sanitization paths injects a #GP fault, and incorrectly delivers it twice to the guest. This causes the guest kernel to observe a kernel-privilege #GP fault (typically fatal) rather than a user-privilege #GP fault (usually converted into SIGSEGV/etc.). Malicious or buggy userspace can crash the guest kernel, resulting in a VM Denial of Service. All versions of Xen from 3.2 onwards are vulnerable. Only x86 systems are vulnerable. ARM platforms are not vulnerable. Only x86 systems that support the SYSENTER instruction in 64bit mode are vulnerable. This is believed to be Intel, Centaur, and Shanghai CPUs. AMD and Hygon CPUs are not believed to be vulnerable. Only x86 PV guests can exploit the vulnerability. x86 PVH / HVM guests cannot exploit the vulnerability.

Weakness: CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component)

## Which versions are affected by CVE-2020-25596?

It affects 4 products.


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

## How do I fix CVE-2020-25596?

Apply the vendor's patch.

## Is CVE-2020-25596 being exploited?

There is no known exploitation of CVE-2020-25596 in the wild and no public exploit code.

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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-2020-25596 and fix it if it is affected.

What it is: CVE-2020-25596 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 23 Sep 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-2020-25596 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-2020-25596/ (Markdown: https://insights.sbomify.com/CVE-2020-25596/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-25596
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-25596
- OSV: https://osv.dev/vulnerability/CVE-2020-25596

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-25596/
Summaries are generated and may contain mistakes; the official description above is the record.