CVE-2018-12892 : Vulnerability Insights and Analysis

A vulnerability was discovered in Xen versions 4.7 through 4.10.x where libxl fails to correctly transmit the readonly flag to qemu during the setup of a SCSI disk, potentially allowing malicious guest administrators to write on intended read-only disk images.

Understanding CVE-2018-12892

What is CVE-2018-12892?

The vulnerability arises from an error in passing the readonly flag to qemu, affecting emulated SCSI disks in systems using qemu-xen with libxl or libxl-based toolstacks.

The Impact of CVE-2018-12892

The vulnerability enables unauthorized write access to supposedly read-only disk images by malicious guest administrators in specific system configurations.

Technical Details of CVE-2018-12892

Vulnerability Description

Libxl fails to correctly transmit the readonly flag to qemu during SCSI disk setup due to a merge conflict resolution error.
Only affects emulated SCSI disks specified as "sd" in the libxl disk configuration.
Limited to systems using qemu-xen with libxl or libxl-based toolstacks.

Affected Systems and Versions

Vulnerable in Xen versions 4.7 through 4.10.x, excluding versions with the XSA-142 patch.
Only impacts systems using qemu-xen with libxl or libxl-based toolstacks.

Exploitation Mechanism

Requires control of the guest kernel or guest kernel command line by a malicious guest administrator.

Mitigation and Prevention

Immediate Steps to Take

Apply patches provided by Xen to address the vulnerability.
Regularly monitor and update Xen software to mitigate potential risks.

Long-Term Security Practices

Implement strict access controls and permissions within virtualized environments.
Conduct regular security audits and assessments to identify and address vulnerabilities.

Patching and Updates

Stay informed about security advisories and updates from Xen to promptly apply patches and fixes.