Denial of Service (DoS) Vulnerability in Xen
Summary
CVE-2020-29567: An issue was discovered in Xen 4.14.x. Affects xen versions < 4.14.1-r0. Fixed in 4.14.1-r0. How to fix ↓
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Background
Xen is an open-source hypervisor that allows multiple operating systems to run on a single host machine. It provides virtualization capabilities and is widely used in cloud computing environments. The vulnerability, identified as CVE-2020-29567, affects Xen versions 4.14.x on x86 systems. It specifically impacts guests with physical PCI devices passed through to them, potentially leading to a Denial of Service (DoS) attack on the entire host.
Vulnerability Detail
The vulnerability arises when IRQ vectors are dynamically allocated and de-allocated on CPUs during the load distribution of IRQ handling. The de-allocation process is triggered when certain conditions are met. However, if these conditions are not initially satisfied, the checking CPU may send an interrupt to itself, expecting that the IRQ will be delivered only after the condition preventing the cleanup has cleared. In the case of two specific IRQ vectors, this expectation is violated, resulting in a continuous stream of self-interrupts that render the CPU effectively unusable. Exploiting this vulnerability, a domain with a passed-through PCI device can cause a lockup of a physical CPU, leading to a DoS attack on the entire host. It's important to note that only x86 systems are vulnerable, while Arm systems remain unaffected.
How To Fix
Minimum fixed version
4.14.1-r0
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
No known workarounds are available for this vulnerability. It is essential to apply the recommended fix by updating Xen to the patched version.
Conclusion
The Denial of Service (DoS) vulnerability in Xen (CVE-2020-29567) affects x86 systems running Xen versions 4.14.x. It allows a guest with a passed-through PCI device to cause a lockup of a physical CPU, resulting in a DoS attack on the entire host. To mitigate this vulnerability, it is essential to update Xen to version 4.14.1-r0 or later. Regularly updating and maintaining software is crucial for ensuring the security of the system. For further support on vulnerability remediation, please contact DevNack.com.
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FAQ
Only x86 systems running Xen versions 4.14.x are affected. Arm systems are not vulnerable.
The vulnerability allows a guest with a passed-through PCI device to cause a lockup of a physical CPU, resulting in a Denial of Service (DoS) attack on the entire host.
No, there are no known workarounds for this vulnerability. Updating Xen to the patched version is the recommended solution.
You can use the Vulert Playground at Vulert Scanner to check if your system is affected by this vulnerability. Simply upload your manifest file (e.g., package-lock.json) to the playground, and it will provide real-time alerts for open-source vulnerabilities.
The recommended mitigation strategy is to update Xen to version 4.14.1-r0 or later. Regularly applying security updates and maintaining up-to-date software is crucial to protect against known vulnerabilities.
References
Related vulnerabilities
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