CVE-2020-17376 Explained : Impact and Mitigation

An issue was discovered in Guest.migrate in virt/libvirt/guest.py in OpenStack Nova before 19.3.1, 20.x before 20.3.1, and 21.0.0. By performing a soft reboot of an instance that has previously undergone live migration, a user may gain access to destination host devices that share the same paths as host devices previously referenced by the virtual machine on the source host. This can include block devices that map to different Cinder volumes at the destination than at the source. Only deployments allowing host-based connections (for instance, root and ephemeral devices) are affected.

Understanding CVE-2020-17376

This section provides insights into the nature and impact of the CVE-2020-17376 vulnerability.

What is CVE-2020-17376?

CVE-2020-17376 is a vulnerability found in Guest.migrate in virt/libvirt/guest.py in OpenStack Nova, affecting versions before 19.3.1, 20.x before 20.3.1, and 21.0.0. It allows a user to access destination host devices after a soft reboot of an instance that has undergone live migration.

The Impact of CVE-2020-17376

The vulnerability enables unauthorized access to destination host devices that share paths with devices referenced by the virtual machine on the source host. This can lead to exposure of block devices mapping to different Cinder volumes at the destination.

Technical Details of CVE-2020-17376

This section delves into the technical aspects of the CVE-2020-17376 vulnerability.

Vulnerability Description

The vulnerability in Guest.migrate in virt/libvirt/guest.py in OpenStack Nova allows users to gain access to destination host devices post soft reboot of a previously live-migrated instance.

Affected Systems and Versions

OpenStack Nova versions before 19.3.1, 20.x before 20.3.1, and 21.0.0

Exploitation Mechanism

The vulnerability occurs when a user performs a soft reboot of an instance that has undergone live migration, allowing access to destination host devices.

Mitigation and Prevention

In this section, we outline steps to mitigate and prevent exploitation of CVE-2020-17376.

Immediate Steps to Take

Upgrade OpenStack Nova to version 19.3.1, 20.3.1, or 21.0.0 to address the vulnerability.
Monitor and restrict access to host devices to prevent unauthorized access.

Long-Term Security Practices

Implement network segmentation to isolate critical systems.
Regularly audit and review access controls to prevent unauthorized access.

Patching and Updates

Apply patches provided by OpenStack Nova to fix the vulnerability and enhance system security.