CVE-2019-19578 : Security Advisory and Response
Discover how CVE-2019-19578 impacts Xen versions up to 4.12.x, allowing x86 PV guest OS users to create degenerate chains of linear pagetables, leading to a denial of service. Learn about the affected systems, exploitation mechanism, and mitigation steps.
A flaw has been discovered in Xen versions up to 4.12.x, allowing x86 PV guest OS users to cause a denial of service by creating degenerate chains of linear pagetables. This issue is a result of an incorrect fix for CVE-2017-15595.
Understanding CVE-2019-19578
This CVE pertains to a vulnerability in Xen that can be exploited by x86 PV guest OS users to trigger a denial of service attack.
What is CVE-2019-19578?
CVE-2019-19578 is a vulnerability in Xen versions up to 4.12.x that enables x86 PV guest OS users to disrupt service by generating degenerate chains of linear pagetables.
The Impact of CVE-2019-19578
- The vulnerability allows malicious or faulty PV guests to crash the hypervisor, leading to a Denial of Service (DoS) affecting the entire host.
- Privilege escalation and information leaks cannot be ruled out.
- This vulnerability affects all versions of Xen on x86 systems, while Arm systems remain unaffected.
Technical Details of CVE-2019-19578
This section provides detailed technical insights into the vulnerability.
Vulnerability Description
- Xen's limited support for linear pagetables can be exploited to create loops or arbitrary chains, causing a crash in the hypervisor.
Affected Systems and Versions
- All versions of Xen on x86 systems are vulnerable.
- Arm systems are not impacted.
- Only x86 PV guests can exploit this vulnerability; x86 HVM and PVH guests are not affected.
Exploitation Mechanism
- Linear pagetables must be enabled for a system to be vulnerable.
- Disabling linear pagetables mitigates the vulnerability.
Mitigation and Prevention
Learn how to protect your systems from CVE-2019-19578.
Immediate Steps to Take
- Disable linear pagetables by selecting CONFIG_PV_LINEAR_PT=n during hypervisor build or adding pv-linear-pt=false in the command-line.
Long-Term Security Practices
- Regularly update Xen to the latest version to patch known vulnerabilities.
Patching and Updates
- Stay informed about security advisories and apply patches promptly to secure your systems.