CVE-2021-29969 : Exploit Details and Defense Strategies

This article provides insights into CVE-2021-29969, a vulnerability affecting Thunderbird versions prior to 78.12 that could allow an attacker to manipulate IMAP server responses.

Understanding CVE-2021-29969

CVE-2021-29969 is a security vulnerability in Thunderbird versions < 78.12 that could be exploited by injecting IMAP server responses before the completion of the STARTTLS handshake.

What is CVE-2021-29969?

If Thunderbird was configured to use STARTTLS for an IMAP connection, and an attacker injected IMAP server responses prior to the completion of the STARTTLS handshake, the injected data was not ignored. This could lead to Thunderbird displaying incorrect information, enabling attackers to manipulate the display of folders that do not exist on the IMAP server.

The Impact of CVE-2021-29969

The vulnerability could have allowed threat actors to deceive Thunderbird users by presenting false information, potentially leading to confusion and manipulative practices.

Technical Details of CVE-2021-29969

CVE ID: CVE-2021-29969 Published Date: 2021-08-05 Updated Date: 2022-08-10 Severity: Medium Affected Version: Thunderbird < 78.12

Vulnerability Description

The vulnerability stemmed from Thunderbird's failure to disregard injected IMAP server responses during the STARTTLS handshake, exposing users to potential misinformation.

Affected Systems and Versions

Thunderbird versions earlier than 78.12 were susceptible to this security flaw, especially if configured to use STARTTLS for IMAP connections.

Exploitation Mechanism

By injecting malicious IMAP server responses before the completion of STARTTLS, an attacker could trick Thunderbird into displaying inaccurate folder information to users.

Mitigation and Prevention

Taking immediate action and adopting long-term security practices can help safeguard against CVE-2021-29969.

Immediate Steps to Take

Update Thunderbird to version 78.12 or later to patch the vulnerability.
Be cautious while accessing emails and verify the authenticity of received messages.

Long-Term Security Practices

Regularly update Thunderbird and other software to stay protected against known vulnerabilities.
Train users to recognize phishing attempts and suspicious activity in emails.

Patching and Updates

Stay informed about security advisories from Mozilla and promptly apply patches and updates to ensure the security of your Thunderbird client.