# CVE-2020-11739: Race condition in n/a

> A malicious guest OS can exploit missing memory barriers in Xen read-write locks to cause denial of service, leak memory, or potentially escalate privileges.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:H/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:** 14 Apr 2020
- **Updated:** 4 Aug 2024
- **Also known as:** ALPINE-CVE-2020-11739, DEBIAN-CVE-2020-11739, GHSA-5wwp-3576-jfjc, UBUNTU-CVE-2020-11739

## What is CVE-2020-11739?

CVE-2020-11739 is a high-severity vulnerability in Debian Debian Linux, published on 14 Apr 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 guest OS users to cause a denial of service or possibly gain privileges because of missing memory barriers in read-write unlock paths. The read-write unlock paths don't contain a memory barrier. On Arm, this means a processor is allowed to re-order the memory access with the preceding ones. In other words, the unlock may be seen by another processor before all the memory accesses within the "critical" section. As a consequence, it may be possible to have a writer executing a critical section at the same time as readers or another writer. In other words, many of the assumptions (e.g., a variable cannot be modified after a check) in the critical sections are not safe anymore. The read-write locks are used in hypercalls (such as grant-table ones), so a malicious guest could exploit the race. For instance, there is a small window where Xen can leak memory if XENMAPSPACE_grant_table is used concurrently. A malicious guest may be able to leak memory, or cause a hypervisor crash resulting in a Denial of Service (DoS). Information leak and privilege escalation cannot be excluded.

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

## Which versions are affected by CVE-2020-11739?

It affects 4 products.


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

## How do I fix CVE-2020-11739?

Apply the vendor's patch.

## Is CVE-2020-11739 being exploited?

There is no known exploitation of CVE-2020-11739 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [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-2020-11739 and fix it if it is affected.

What it is: CVE-2020-11739 is a high-severity vulnerability in Debian Debian Linux, published on 14 Apr 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-2020-11739 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-2020-11739/ (Markdown: https://insights.sbomify.com/CVE-2020-11739/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-11739
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-11739
- OSV: https://osv.dev/vulnerability/CVE-2020-11739

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-11739/
Summaries are generated and may contain mistakes; the official description above is the record.