CVE-2019-19783 : Security Advisory and Response

Cyrus IMAP before versions 2.5.15, 3.0.x before 3.0.13, and 3.1.x through 3.1.8 is vulnerable to a critical security issue that allows users to exploit sieve script uploading or certain sieve options to gain unauthorized mailbox creation privileges.

Understanding CVE-2019-19783

This CVE identifies a vulnerability in Cyrus IMAP versions that enables users to create mailboxes with administrator privileges.

What is CVE-2019-19783?

An issue in Cyrus IMAP versions prior to 2.5.15, 3.0.x before 3.0.13, and 3.1.x through 3.1.8 allows users to manipulate sieve scripts to create mailboxes with admin rights.

The Impact of CVE-2019-19783

The vulnerability permits unauthorized users to exploit sieve script uploading or specific sieve options to create mailboxes with elevated privileges, posing a significant security risk.

Technical Details of CVE-2019-19783

Cyrus IMAP is susceptible to the following:

Vulnerability Description

Users can leverage sieve scripts to create mailboxes with admin privileges due to mishandling in the autosieve_createfolder() function.

Affected Systems and Versions

Versions prior to 2.5.15, 3.0.x before 3.0.13, and 3.1.x through 3.1.8 of Cyrus IMAP are impacted.

Exploitation Mechanism

Exploitation involves using sieve scripts with a fileinto directive to create mailboxes with administrator rights.

Mitigation and Prevention

To address CVE-2019-19783, consider the following:

Immediate Steps to Take

Update Cyrus IMAP to versions 2.5.15, 3.0.13, or 3.1.8 to mitigate the vulnerability.
Disable sieve script uploading or review and restrict sieve options to prevent unauthorized mailbox creation.

Long-Term Security Practices

Regularly monitor and audit sieve scripts and mailbox creation activities for suspicious behavior.
Educate users on secure scripting practices and the risks associated with unauthorized mailbox creation.

Patching and Updates

Apply patches provided by Cyrus IMAP to address the vulnerability and enhance system security.