CVE-2025-1015: Thunderbird Address Book URI Security Vulnerability - Unsanitized Links Leading to Potential Malicious Payloads

The Mozilla Thunderbird email client is known for its security features and customizability, offering users a reliable and flexible open-source application. However, as with any piece of software, vulnerabilities may arise. One such vulnerability exists in versions prior to Thunderbird 128.7 and 135, designated as CVE-2025-1015. In this post, we will discuss the nature of the vulnerability, provide a code snippet, and direct the reader to original sources and references.

Vulnerability Details

The vulnerability CVE-2025-1015 revolves around the Thunderbird Address Book feature, specifically the URI fields. These fields have been found to contain unsanitized links, which could potentially be exploited by attackers to facilitate the deployment of malicious payloads. A key concern is that an attacker could create and export an address book containing a malicious payload in a field, such as the “Other” field of the Instant Messaging section.

If another user were to import the attacker's address book and click on the unsanitized link, the action could lead to the triggering of an unprivileged JavaScript execution inside the Thunderbird application. Consequently, this may result in adverse effects on the user's software environment and information security.

Code Snippet

Here's a code snippet demonstrating the structure of an address book entry with the potentially malicious payload in the URI field of the Instant Messaging section:

{
  "firstName": "John",
  "lastName": "Doe",
  "email": "johndoe@example.com",
  "instantMessaging": {
    "other": "javascript:/*MALICIOUS_PAYLOAD_GOES_HERE*/"
  }
}

The malicious payload would replace the /*MALICIOUS_PAYLOAD_GOES_HERE*/ placeholder in the example above.

Original References

For more detailed information on this vulnerability, readers are encouraged to visit the official sources:

1. Mozilla Foundation Security Advisory: MFSA2025-38
2. Mozilla Bugzilla: Bug 202516

Exploit Details

An attacker exploiting this vulnerability would need to create a malicious address book containing the unsanitized link and ensure its distribution to other Thunderbird users, leading them to import it into their own email clients. By clicking on the embedded link, users inadvertently open a web page within the Thunderbird application that runs potentially harmful JavaScript code.

Mitigations

Users of Thunderbird should promptly update their software to at least version 128.7 or 135 to address this vulnerability. It is also advisable for users to routinely update their software applications to protect against new and emerging threats. Careful inspection of address books before importing them may help to identify suspicious or unexpected entries.

Timeline

Published on: 02/04/2025 14:15:32 UTC
Last modified on: 03/10/2025 19:15:39 UTC