CVE-2021-28710 : What You Need to Know
Discover details about CVE-2021-28710, a Xen vulnerability that allows malicious guests to escalate privileges. Learn about affected systems, impact, and mitigation steps.
A vulnerability has been identified in Xen, specifically affecting certain VT-d IOMMUs, which could allow a malicious guest to escalate its privileges to that of the host.
Understanding CVE-2021-28710
This CVE, assigned to Xen, was discovered by Jan Beulich of SUSE. It impacts Xen versions less than 4.12, version 4.15.x, and next of xen-unstable.
What is CVE-2021-28710?
certain VT-d IOMMUs may not work in shared page table mode. For efficiency reasons, address translation control structures (page tables) may be shared between CPUs and IOMMUs. An IOMMU may require fewer page table levels than allocated, leading to a privilege escalation vulnerability.
The Impact of CVE-2021-28710
This vulnerability allows a malicious guest to potentially elevate its privileges to match that of the host, posing a serious security risk to the system.
Technical Details of CVE-2021-28710
The vulnerability lies in Xen's handling of shared page tables, skipping essential stripping of page table levels when necessary. This oversight enables guests to write to critical page table entries.
Vulnerability Description
certain VT-d IOMMUs may not work in shared page table mode. Xen failed to strip page table levels appropriately, allowing guests to modify crucial page table entries.
Affected Systems and Versions
Xen versions less than 4.12, version 4.15.x, and next of xen-unstable are impacted by this vulnerability.
Exploitation Mechanism
A malicious guest with access to shared page tables can leverage this flaw to potentially escalate its privileges to match that of the host.
Mitigation and Prevention
By implementing immediate steps and long-term security practices, users can safeguard their systems from this vulnerability.
Immediate Steps to Take
To mitigate the risk, suppress the use of shared page tables by passing "iommu=no-sharept" on the hypervisor command line globally or using the "passthrough=sync_pt" xl guest configuration file option per guest.
Long-Term Security Practices
Regularly update and patch Xen to ensure the latest security fixes are in place. Additionally, monitor for any suspicious activities that could indicate an exploit of this vulnerability.
Patching and Updates
Stay informed about security advisories from Xen and apply patches promptly to address known vulnerabilities.