CVE-2021-28687 : Vulnerability Insights and Analysis
Discover how CVE-2021-28687 impacts Xen versions 4.12 through 4.14. Uninitialized data structures in Xen's toolstack libxl can lead to crashes, potentially causing a denial-of-service.
This CVE-2021-28687 vulnerability affects Xen versions 4.12 through 4.14. An issue was discovered by Olaf Hering where HVM soft-reset crashes toolstack libxl due to uninitialized data structures, leading to a denial-of-service risk. The impact varies depending on the toolstack used.
Understanding CVE-2021-28687
CVE-2021-28687 is a vulnerability in Xen versions 4.12 through 4.14 that allows a malicious guest to crash the management daemon, potentially causing a denial-of-service attack.
What is CVE-2021-28687?
The vulnerability arises from uninitialized data structures within the libxl toolstack, specifically affecting the 'soft reset' feature and leading to crashes in the monitoring process of the guest.
The Impact of CVE-2021-28687
A malicious guest can trigger a denial-of-service attack on the management daemon, causing disruptions to ongoing operations and potentially affecting the entire system.
Technical Details of CVE-2021-28687
The vulnerability in the libxl__domain_suspend_state structure allows an attacker to exploit the 'soft reset' path, leading to a crash in the monitoring process of the guest.
Vulnerability Description
The uninitialized data structure can result in an assert() call when accessed, crashing the guest monitoring process.
Affected Systems and Versions
Xen versions 4.12 through 4.14 are affected. Systems using daemon-based toolstacks like libvirt are more vulnerable to system-wide denial-of-service.
Exploitation Mechanism
By initiating a 'soft reboot', a guest can exploit the uninitialized data structure in libxl, leading to crashes in the toolstack monitoring the guest.
Mitigation and Prevention
To mitigate CVE-2021-28687, immediate response steps include automatically restarting management daemons post-crash and implementing security best practices.
Immediate Steps to Take
Ensure that any management daemons are set to restart automatically after a crash to minimize downtime and performance impacts.
Long-Term Security Practices
Regularly update and patch Xen software installations to prevent exploitation of known vulnerabilities and maintain system security.
Patching and Updates
Stay informed about security updates and patches released by Xen to address vulnerabilities like CVE-2021-28687.