Vulnerability in Xen Package: CVE-2021-28710
Summary
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 (and, on suitable hardware, by default will) be shared between CPUs, for second-... Affects xen versions < 4.15.1-r1. Fixed in 4.15.1-r1. How to fix ↓
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Background
The Xen package is an open-source hypervisor that provides virtualization services for various operating systems. It allows multiple guest operating systems to run on a single host system, enabling efficient resource utilization. However, a vulnerability has been discovered in certain versions of Xen that can lead to unauthorized write access to leaf page table entries in shared page table mode.
Vulnerability Detail
The vulnerability (CVE-2021-28710) arises from a flaw in the handling of address translation control structures (page tables) in Xen's VT-d IOMMUs. In shared page table mode, where page tables are shared between CPUs and IOMMUs, Xen fails to strip the top-level table when it is not required by the IOMMU. This oversight allows a guest to modify leaf page table entries, potentially leading to privilege escalation or other security breaches.
How To Fix
Minimum fixed version
4.15.1-r1
This is the first release that contains the fix.
sudo apk add --upgrade xenTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If updating the Xen package is not immediately feasible, a temporary workaround is to disable shared page table mode. This can be achieved by modifying the Xen configuration to use separate page tables for CPUs and IOMMUs. However, this workaround may impact performance and should only be considered as a temporary measure until the package can be updated.
Conclusion
The vulnerability in the Xen package (CVE-2021-28710) exposes a potential security risk in shared page table mode. It is crucial to update the package to the recommended version or apply the provided workaround to mitigate the vulnerability. For further assistance in vulnerability remediation, please contact DevNack.com.
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FAQ
Xen is an open-source hypervisor that allows multiple guest operating systems to run on a single host system.
The vulnerability can allow a guest operating system to modify leaf page table entries, potentially leading to privilege escalation or other security breaches.
The vulnerability affects Xen versions prior to 4.15.1-r1.
To fix the vulnerability, update the Xen package to version 4.15.1-r1 or later.
Yes, a temporary workaround is to disable shared page table mode in the Xen configuration.
References
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