CVE-2019-18423 : Security Advisory and Response

A vulnerability was found in Xen versions up to 4.12.x, allowing denial of service attacks by malicious ARM guest operating system users through a XENMEM_add_to_physmap hypercall.

Understanding CVE-2019-18423

This CVE identifies a vulnerability in Xen that affects ARM systems, enabling a denial of service attack.

What is CVE-2019-18423?

This vulnerability in Xen versions up to 4.12.x allows malicious ARM guest OS users to trigger a denial of service by exploiting a specific hypercall.

The Impact of CVE-2019-18423

The vulnerability enables a malicious guest administrator to crash the hypervisor, leading to a denial of service (DoS) attack.
Only Arm systems are vulnerable, while x86 systems remain unaffected.

Technical Details of CVE-2019-18423

This section delves into the technical aspects of the vulnerability.

Vulnerability Description

The issue arises from the improper handling of p2m->max_mapped_gfn in Xen functions, leading to a crash in the hypervisor.

Affected Systems and Versions

Xen versions up to 4.12.x are impacted by this vulnerability.

Exploitation Mechanism

By crafting a specific XENMEM_add_to_physmap hypercall followed by accessing an address, a malicious user can trigger the vulnerability.

Mitigation and Prevention

Protecting systems from CVE-2019-18423 involves taking immediate steps and implementing long-term security practices.

Immediate Steps to Take

Apply patches provided by Xen to address the vulnerability.
Monitor for any suspicious activities on the system.

Long-Term Security Practices

Regularly update Xen and other software to patch known vulnerabilities.
Implement access controls to limit the impact of potential attacks.

Patching and Updates

Stay informed about security updates from Xen and apply them promptly to secure the system.