CVE-2021-28698 : Security Advisory and Response
Learn about CVE-2021-28698, a Xen vulnerability allowing DoS attacks by guest kernels. Understand the impact, affected systems, and mitigation strategies.
This article provides an overview of CVE-2021-28698, detailing the vulnerability, its impact, affected systems, and mitigation strategies.
Understanding CVE-2021-28698
CVE-2021-28698 is a vulnerability in Xen that allows malicious or buggy guest kernels to launch a Denial of Service (DoS) attack on the entire system.
What is CVE-2021-28698?
The vulnerability stems from long-running loops in grant table handling within Xen. When processing certain actions, Xen iterates over grant mapping entries, even those no longer in use. This can cause CPU starvation, impacting system performance.
The Impact of CVE-2021-28698
Malicious or buggy guest kernels can exploit this vulnerability to mount a DoS attack, affecting the system's overall performance and stability.
Technical Details of CVE-2021-28698
CVE-2021-28698 affects multiple versions of Xen, including 4.11.x, 4.12.x, 4.13.x, 4.14.x, and 4.15.x. This vulnerability poses a risk to systems running Xen with default settings.
Vulnerability Description
Xen's grant table handling may lead to CPU overutilization, resulting in system performance issues and potential DoS attacks.
Affected Systems and Versions
Xen versions 4.11.x, 4.12.x, 4.13.x, 4.14.x, and 4.15.x are impacted by CVE-2021-28698, with systems running default settings at risk.
Exploitation Mechanism
Malicious or faulty guest kernels can exploit this vulnerability within Xen, potentially causing a system-wide DoS attack.
Mitigation and Prevention
To mitigate the risks associated with CVE-2021-28698, immediate steps and long-term security practices are recommended.
Immediate Steps to Take
Reducing the number of grant mappings in Xen can help prevent the exploitation of this vulnerability. Configuring specific settings, such as 'gnttab_max_maptrack_frames=256,' can enhance system security.
Long-Term Security Practices
Regularly updating Xen and implementing secure configurations are essential for maintaining system integrity and preventing DoS attacks.
Patching and Updates
Stay informed about security advisories and patch updates released by Xen to address CVE-2021-28698 and other potential vulnerabilities.