CVE-2021-28691 Explained : Impact and Mitigation
Learn about CVE-2021-28691, a guest-triggered use-after-free vulnerability in Linux xen-netback allowing a malicious or buggy network PV frontend to crash dom0 with potential privilege escalation.
A guest-triggered use-after-free vulnerability in Linux xen-netback allows a malicious or buggy network PV frontend to disable the interface, leading to a crash. This CVE can result in a dom0 crash, with potential privilege escalation and information leaks.
Understanding CVE-2021-28691
This CVE pertains to a vulnerability in Linux xen-netback that can be exploited by a malicious network PV frontend.
What is CVE-2021-28691?
A malicious or buggy network PV frontend can force Linux netback to disable the interface and terminate the receive kernel thread associated with queue 0, triggering a use-after-free vulnerability in Linux netback upon backend destruction.
The Impact of CVE-2021-28691
The vulnerability can allow a malicious frontend driver to crash the dom0, potentially leading to privilege escalation and information leakage.
Technical Details of CVE-2021-28691
This section provides a deeper insight into the vulnerability.
Vulnerability Description
A malicious or buggy frontend driver can trigger a dom0 crash, possibly resulting in privilege escalation and information leaks.
Affected Systems and Versions
Systems using Linux version 5.5 or newer are vulnerable to this CVE.
Exploitation Mechanism
A malicious network PV frontend can exploit this vulnerability by forcing Linux netback to disable the interface, causing a kernel thread termination and subsequent use-after-free in Linux netback.
Mitigation and Prevention
It is crucial to take immediate steps to address and prevent the exploitation of this vulnerability.
Immediate Steps to Take
On x86 systems, running only HVM guests with emulated network cards can help avoid the issue. However, there is currently no option in the upstream toolstack to offer only emulated network cards to guests.
Long-Term Security Practices
Implementing robust security measures, regular security assessments, and staying informed about relevant patches and updates are essential for long-term security.
Patching and Updates
Ensuring timely application of security patches and updates is critical to mitigating the risks associated with CVE-2021-28691.