CVE-2021-21284 : Exploit Details and Defense Strategies

A privilege escalation vulnerability has been discovered in Moby, impacting versions prior to 19.03.15 and between 20.0.0 to 20.10.3. Attackers can exploit the --userns-remap option to escalate privileges, potentially leading to unauthorized access.

Understanding CVE-2021-21284

This section provides insights into the nature of the vulnerability, its impact, technical details, and recommended mitigation strategies.

What is CVE-2021-21284?

The vulnerability in Docker's Moby software allows attackers to gain unauthorized access by exploiting the --userns-remap option. By manipulating user namespace remapping, threat actors can escalate privileges, resulting in potential security breaches and unauthorized system access.

The Impact of CVE-2021-21284

The privilege escalation vulnerability poses a significant risk to systems running affected versions of Moby. Unauthorized users could exploit this vulnerability to gain elevated privileges, execute arbitrary code, or access sensitive information, potentially leading to severe security implications.

Technical Details of CVE-2021-21284

Understanding the technical aspects of the vulnerability, affected systems, and exploitation methods is crucial in implementing effective mitigation strategies.

Vulnerability Description

In Docker versions prior to 19.03.15 and between 20.0.0 to 20.10.3, a flaw in the --userns-remap option allows unauthorized privilege escalation, granting attackers real root access. This could lead to unauthorized modifications and potential security breaches within the container environment.

Affected Systems and Versions

The vulnerability impacts Moby versions earlier than 19.03.15 and versions ranging from 20.0.0 to 20.10.3. Systems running these versions are susceptible to privilege escalation attacks via the --userns-remap option.

Exploitation Mechanism

By exploiting the --userns-remap option, threat actors can abuse user namespace remapping to escalate privileges from remapped root to real root. This manipulation enables unauthorized users to bypass security restrictions and gain elevated access within the container environment.

Mitigation and Prevention

To safeguard systems against CVE-2021-21284 and mitigate potential risks, immediate actions and long-term security practices are essential.

Immediate Steps to Take

Update Docker to versions 19.03.15 or 20.10.3 to apply necessary security patches.
Restrict access to critical system files and directories to minimize the impact of privilege escalation.
Monitor system logs for any suspicious activities indicating unauthorized access.

Long-Term Security Practices

Implement least privilege access controls to limit user permissions and reduce the attack surface.
Regularly audit and update container images and dependencies to address known vulnerabilities.
Conduct security assessments and penetration testing to proactively identify and address security gaps.

Patching and Updates

Ensure timely installation of security patches and updates released by Docker to address vulnerabilities and strengthen the security posture of Moby installations.