CVE-2022-24838 : Security Advisory and Response

Nextcloud Calendar is a calendar application for the nextcloud framework that is impacted by a Command Injection vulnerability allowing attackers to inject arbitrary SMTP commands via Appointment Emails.

Understanding CVE-2022-24838

This vulnerability, tracked as CVE-2022-24838, affects Nextcloud Calendar versions prior to 3.2.2. It enables malicious actors to exploit newlines in the email values of JSON requests to manipulate SMTP commands.

What is CVE-2022-24838?

CVE-2022-24838 is a Command Injection vulnerability in Nextcloud Calendar that arises due to insufficient sanitization of newlines and special characters in email values. This allows attackers to inject arbitrary SMTP commands by breaking out of the 'RCPT TO:<BOOKING USER'S EMAIL> ' SMTP command.

The Impact of CVE-2022-24838

With a CVSS base score of 5.3, this vulnerability has a medium severity rating. Attackers can leverage this flaw to execute unauthorized SMTP commands, potentially leading to unauthorized access or other malicious activities.

Technical Details of CVE-2022-24838

Vulnerability Description

The vulnerability stems from the lack of proper sanitization of special characters, allowing injection of newlines in email values to manipulate SMTP commands.

Affected Systems and Versions

Nextcloud Calendar versions earlier than 3.2.2 are affected by this vulnerability.

Exploitation Mechanism

Malicious actors can exploit this vulnerability by injecting newlines in appointment emails to execute unauthorized SMTP commands.

Mitigation and Prevention

Immediate Steps to Take

It is crucial to upgrade Nextcloud Calendar to version 3.2.2 or newer to mitigate the risk of exploitation. Ensure all systems are promptly updated to prevent potential command injections via appointment emails.

Long-Term Security Practices

Implement strict input validation mechanisms to sanitize user input effectively and prevent injection attacks in the future. Regularly monitor security advisories and promptly apply patches and updates to address known vulnerabilities.

Patching and Updates

Refer to the following URLs for more information and to access the necessary patches:

Nextcloud Security Advisories
Nextcloud Calendar Pull Request
Nextcloud Calendar Commit Details