What is the CVSS score of CVE-2020-11739?

CVE-2020-11739 has a CVSS 3.1 base score of 7.8 (High). CVSS vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H. EPSS exploitation probability: 0.3%.

Is there a patch available for CVE-2020-11739?

Yes, a patch is available for CVE-2020-11739. Update the affected software to the latest version immediately.

Debian Linux CVE-2020-11739

HIGH

Race Condition (CWE-362)

2020-04-14 cve@mitre.org

Privilege Escalation Denial Of Service Race Condition Debian Debian Linux Fedora Leap Xen Opensuse Fedoraproject

7.8

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

7.8 HIGH

AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Local

Attack Complexity

High

Privileges Required

Low

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

CVE Published

Apr 14, 2020 - 13:15 nvd

HIGH 7.8

DescriptionNVD

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.

AnalysisAI

Technical ContextAI

This vulnerability is classified under CWE-362. 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. Affected products include: Xen, Fedoraproject Fedora, Debian Debian Linux, Opensuse Leap. Version information: through 4.13..

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.