CVE-2021-27216 Explained : Impact and Mitigation

Exim 4 before 4.94.2 has a vulnerability that allows local users to delete arbitrary files as root. This CVE involves a race condition with certain options.

Understanding CVE-2021-27216

This CVE relates to a privilege escalation vulnerability in Exim 4 versions before 4.94.2.

What is CVE-2021-27216?

CVE-2021-27216 is an issue in Exim 4 that allows a local user to delete files as root by exploiting a specific race condition.

The Impact of CVE-2021-27216

The vulnerability can lead to unauthorized deletion of files on the system, potentially causing a loss of data or disrupting system operations.

Technical Details of CVE-2021-27216

This section outlines the specific technical aspects of the CVE.

Vulnerability Description

The vulnerability in Exim 4 before version 4.94.2 allows a local user to delete arbitrary files as root by leveraging a delete_pid_file race condition.

Affected Systems and Versions

All Exim 4 versions before 4.94.2 are affected by this vulnerability.

Exploitation Mechanism

The exploitation involves using certain options (-oP and -oPX) to exploit the delete_pid_file race condition.

Mitigation and Prevention

To secure your system from CVE-2021-27216, follow these mitigation steps.

Immediate Steps to Take

Upgrade Exim to version 4.94.2 or newer.
Monitor and restrict local user access to critical system files.

Long-Term Security Practices

Regularly update Exim and other software components to patch known vulnerabilities.
Implement least privilege access controls to limit user capabilities.

Patching and Updates

Stay informed about security updates for Exim and apply patches promptly to protect your system.