CVE-2022-4055

When xdg-mail is configured to use thunderbird for mailto URLs, improper parsing of the URL can lead to additional headers being passed to thunderbird that should not be included per RFC 2368. An attacker can use this method to create a mailto URL that looks safe to users, but will actually attach files when clicked.

To exploit this flaw, an attacker would need to convince a user to click on a specially crafted mailto URL. Additionally, the user must have the Thunderbird email client installed and xdg-mail configured to use Thunderbird to handle mailto URLs. Therefore, this vulnerability is rated as moderate rather than important because it requires user interaction and specific system configurations.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this flaw, either:

1. Do not use mailto links at all
2. Always double-check in the user interface that there are no unwanted attachments before sending emails; especially when the email originates from clicking a mailto link.