CVE-2023-28623 : Security Advisory and Response

This CVE involves unauthorized users being able to register an account in specific configurations in Zulip, an open-source team collaboration tool. The issue is related to improper authorization and missing authorization, impacting the confidentiality and integrity of affected systems.

Understanding CVE-2023-28623

This vulnerability in Zulip allows an attacker to create a new account in an organization with specific configurations, bypassing proper authorization checks. By exploiting this issue, an unauthorized user can register an account with an arbitrary email address under certain conditions.

What is CVE-2023-28623?

CVE-2023-28623 involves a scenario where certain authentication backends are enabled in Zulip's settings, specifically related to LDAP authentication. If the organization's permissions do not require invitations to join and a specific combination of authentication backends is in place, an attacker can create a new account with an unauthorized email address.

The Impact of CVE-2023-28623

The impact of this vulnerability is significant for systems running Zulip versions equal to or greater than 2.1.0 and less than 6.2. It jeopardizes the confidentiality of user data and the integrity of the organization's authentication processes. Immediate action is required to mitigate any potential exploitation.

Technical Details of CVE-2023-28623

This section delves into the specifics of the vulnerability, including its description, affected systems and versions, and the exploitation mechanism.

Vulnerability Description

The vulnerability arises due to improper authorization checks in Zulip when certain authentication backends are configured and organization permissions do not require invitations to join. This allows unauthorized users to create accounts with arbitrary email addresses.

Affected Systems and Versions

Zulip versions greater than or equal to 2.1.0 and less than 6.2 are affected by this vulnerability. Specifically, systems with the described combination of authentication backends and organization permissions are at risk.

Exploitation Mechanism

Attackers exploit this vulnerability by leveraging the specific configuration settings within Zulip that bypass proper authorization checks. By creating an account with an unauthorized email address, the attacker can gain unauthorized access to the organization's collaboration platform.

Mitigation and Prevention

To address CVE-2023-28623, it is crucial to take immediate steps to secure affected systems and prevent any unauthorized access or data breaches.

Immediate Steps to Take

Upgrade to Zulip version 6.2 or above, where this vulnerability has been addressed.
If upgrading is not immediately possible, enable the 'Invitations are required for joining this organization' permission to prevent unauthorized registrations.

Long-Term Security Practices

Regularly review and update authentication settings to ensure proper authorization checks are in place.
Implement a robust security policy that includes regular security audits and vulnerability assessments.

Patching and Updates

Stay informed about security updates and patches released by Zulip to address known vulnerabilities. Keep the software up to date to benefit from the latest security enhancements and bug fixes.