CVE-2020-11739

What it is

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.

At a glance

Exploitability

Can be exploited locally on the machine with a low-privilege account. High risk of data exposure, data tampering, service disruption.

Exploit odds

0.3% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2020-04-14 13:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 02:50 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.3% in the next 30 days (EPSS).
• Severity: 7.8 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2020-04-14 13:15 UTC

Last modified

2026-06-17 02:50 UTC

Exploit probability

0.3% · EPSS, next 30 days

Weakness

CWE-362 · Race condition

Record status

Modified

Affected

• Xen ≤ 4.13.0
• Xen 4.13.0
• Fedoraproject Fedora 30
• Fedoraproject Fedora 31
• Fedoraproject Fedora 32
• Debian Linux 10.0
• Opensuse Leap 15.1

Attack profile CVSS 3.1 · 7.8

Attack vector

Local

Complexity

High

Privileges needed

Low

User interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2020-11739.md and follow it. Check whether this project is affected by CVE-2020-11739. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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