CVE-2021-20255 : What You Need to Know

A stack overflow via an infinite recursion vulnerability was found in the eepro100 i8255x device emulator of QEMU, allowing a guest user to crash the QEMU process on the host, resulting in a denial of service.

Understanding CVE-2021-20255

This CVE identifies a stack overflow vulnerability in the eepro100 i8255x device emulator of QEMU, impacting system availability.

What is CVE-2021-20255?

CVE-2021-20255 is a vulnerability in QEMU that allows a guest user or process to trigger a stack overflow via an infinite recursion issue in the device emulator, potentially leading to a denial of service on the host system.

The Impact of CVE-2021-20255

The vulnerability poses a threat to system availability, as a malicious actor could crash the QEMU process on the host, consuming CPU cycles and disrupting normal operations.

Technical Details of CVE-2021-20255

The technical details of CVE-2021-20255 include:

Vulnerability Description

The issue arises due to a stack overflow via an infinite recursion vulnerability in the eepro100 i8255x device emulator of QEMU, specifically while processing controller commands with a DMA reentry problem.

Affected Systems and Versions

All versions of QEMU are affected by this vulnerability.

Exploitation Mechanism

An attacker can exploit this vulnerability to trigger an infinite recursion in the device emulator, leading to a denial of service by crashing the QEMU process on the host.

Mitigation and Prevention

To mitigate the risks associated with CVE-2021-20255, consider the following steps:

Immediate Steps to Take

Update QEMU to the latest patched version to address the stack overflow vulnerability.
Monitor system performance for any unusual CPU consumption that could indicate exploitation.

Long-Term Security Practices

Regularly update and patch all software and dependencies to prevent known vulnerabilities.
Implement network segmentation and access controls to limit the impact of potential attacks.

Patching and Updates

Stay informed about security updates and advisories related to QEMU from reliable sources to apply patches promptly and ensure the security of your systems.