# CVE-2020-15565: Privilege escalation in n/a

> A malicious guest can gain host privileges or cause denial of service due to missing cache write-back during page table splitting in Xen.

- **Severity:** High 8.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/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-2020-15565, DEBIAN-CVE-2020-15565, GHSA-xcjp-mj7m-5f57, UBUNTU-CVE-2020-15565

## What is CVE-2020-15565?

CVE-2020-15565 is a high-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 Intel HVM guest OS users to cause a host OS denial of service or possibly gain privileges because of insufficient cache write-back under VT-d. When page tables are shared between IOMMU and CPU, changes to them require flushing of both TLBs. Furthermore, IOMMUs may be non-coherent, and hence prior to flushing IOMMU TLBs, a CPU cache also needs writing back to memory after changes were made. Such writing back of cached data was missing in particular when splitting large page mappings into smaller granularity ones. A malicious guest may be able to retain read/write DMA access to frames returned to Xen's free pool, and later reused for another purpose. Host crashes (leading to a Denial of Service) and privilege escalation cannot be ruled out. Xen versions from at least 3.2 onwards are affected. Only x86 Intel systems are affected. x86 AMD as well as Arm systems are not affected. Only x86 HVM guests using hardware assisted paging (HAP), having a passed through PCI device assigned, and having page table sharing enabled can leverage the vulnerability. Note that page table sharing will be enabled (by default) only if Xen considers IOMMU and CPU large page size support compatible.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2020-15565?

It affects 4 products.


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

## How do I fix CVE-2020-15565?

Apply the vendor's patch.

## Is CVE-2020-15565 being exploited?

There is no known exploitation of CVE-2020-15565 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-2020-15565 and fix it if it is affected.

What it is: CVE-2020-15565 is a high-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-2020-15565 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-2020-15565/ (Markdown: https://insights.sbomify.com/CVE-2020-15565/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-15565
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-15565
- OSV: https://osv.dev/vulnerability/CVE-2020-15565

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-15565/
Summaries are generated and may contain mistakes; the official description above is the record.