CVE-2020-29484 : Exploit Details and Defense Strategies

An issue was discovered in Xen through 4.14.x where a malicious guest can cause a denial of service by crashing xenstored.

Understanding CVE-2020-29484

This CVE involves a vulnerability in Xen that can be exploited by a malicious guest to crash xenstored, leading to a denial of service.

What is CVE-2020-29484?

The vulnerability allows a guest to register a watch with a large tag, causing xenstored to crash due to a NULL pointer dereference, resulting in a denial of service.

The Impact of CVE-2020-29484

A malicious guest can crash xenstored, leading to a denial of service.
Following a xenstored crash, management operations become impossible.

Technical Details of CVE-2020-29484

This section provides more technical insights into the vulnerability.

Vulnerability Description

Xenstore watch fires trigger xenstore messages containing path and tag information.
Payload length limit of 4096 bytes can be exceeded, leading to an error and potential crash.

Affected Systems and Versions

Xen through version 4.14.x is affected by this vulnerability.

Exploitation Mechanism

By registering a watch with a large tag, a guest can cause xenstored to crash, resulting in a denial of service.

Mitigation and Prevention

Protect systems from the CVE-2020-29484 vulnerability with the following steps:

Immediate Steps to Take

Apply patches provided by Xen to address the vulnerability.
Monitor system logs for any suspicious activity related to xenstored.

Long-Term Security Practices

Regularly update Xen to the latest version to mitigate known vulnerabilities.
Implement proper access controls to limit guest privileges and prevent unauthorized actions.

Patching and Updates

Stay informed about security advisories from Xen and promptly apply patches to secure the system.