CVE-2019-11739 : Exploit Details and Defense Strategies

A security vulnerability in Thunderbird versions older than 68.1 and 60.9 could lead to plaintext disclosure when handling encrypted S/MIME parts in certain messages.

Understanding CVE-2019-11739

This CVE involves a covert content attack on S/MIME encryption using a carefully crafted multipart/alternative message.

What is CVE-2019-11739?

The vulnerability arises from the inclusion of encrypted S/MIME parts in a multipart/alternative message, potentially exposing plaintext when included in an HTML reply or forward.

The Impact of CVE-2019-11739

The security flaw affects Thunderbird versions older than 68.1 and 60.9, potentially leading to inadvertent plaintext disclosure.

Technical Details of CVE-2019-11739

This section provides detailed technical insights into the CVE.

Vulnerability Description

The vulnerability allows for the leakage of plaintext when encrypted S/MIME parts are included in a carefully crafted multipart/alternative message.

Affected Systems and Versions

Product: Thunderbird
Vendor: Mozilla
Affected Versions:
Thunderbird < 68.1
Thunderbird < 60.9

Exploitation Mechanism

The vulnerability can be exploited by including encrypted S/MIME parts in a multipart/alternative message, leading to plaintext exposure in specific scenarios.

Mitigation and Prevention

Protecting systems from CVE-2019-11739 requires immediate actions and long-term security practices.

Immediate Steps to Take

Update Thunderbird to version 68.1 or newer to mitigate the vulnerability.
Avoid opening or replying to suspicious emails with encrypted S/MIME parts.

Long-Term Security Practices

Regularly update Thunderbird and other software to the latest versions.
Educate users on safe email practices to prevent falling victim to similar attacks.

Patching and Updates

Apply security patches provided by Mozilla promptly to address vulnerabilities and enhance system security.