CVE-2019-19583 : Security Advisory and Response

A vulnerability was discovered in Xen versions up to 4.12.x, affecting x86 HVM/PVH guest operating systems. This vulnerability allows users to cause a denial of service by crashing the guest OS due to mishandling of certain cases in the VMX VMEntry checks.

Understanding CVE-2019-19583

This CVE pertains to a specific vulnerability in Xen that impacts guest operating systems using x86 HVM/PVH architecture.

What is CVE-2019-19583?

The vulnerability in Xen versions up to 4.12.x allows users of guest OS utilizing x86 HVM/PVH architecture to cause a denial of service by crashing the guest OS. The issue arises due to mishandling of certain cases in the VMX VMEntry checks.

The Impact of CVE-2019-19583

Users of guest OS can crash the system, leading to a denial of service.
The vulnerability affects all versions of Xen.
Only systems supporting VMX hardware virtual extensions (Intel, Cyrix, or Zhaoxin CPUs) are impacted.
Arm and AMD systems are not affected.
Only HVM/PVH guests are at risk, as PV guests cannot exploit this vulnerability.

Technical Details of CVE-2019-19583

This section provides detailed technical information about the vulnerability.

Vulnerability Description

The issue occurs when a precise combination of states happens during VMX VMEntry checks, leading to a fatal VMEntry failure in the guest OS.

Affected Systems and Versions

All versions of Xen up to 4.12.x are affected.
Systems supporting VMX hardware virtual extensions (Intel, Cyrix, or Zhaoxin CPUs) are vulnerable.
Arm and AMD systems are not impacted.
Only HVM/PVH guests are at risk.

Exploitation Mechanism

Userspace code of HVM/PVH guests can crash the guest OS, resulting in a denial of service.
The vulnerability is triggered by a specific combination of states during VMX VMEntry checks.

Mitigation and Prevention

Protecting systems from CVE-2019-19583 requires immediate steps and long-term security practices.

Immediate Steps to Take

Apply patches and updates provided by Xen to address the vulnerability.
Monitor for any unusual system behavior that could indicate an exploit attempt.

Long-Term Security Practices

Regularly update and patch Xen and other software to prevent known vulnerabilities.
Implement strong access controls and monitoring to detect and mitigate potential threats.

Patching and Updates

Stay informed about security advisories from Xen and promptly apply recommended patches to secure systems.