Thunderbirds handling of the X-Mozilla-External-Attachment-URL header can be exploited to execute JavaScript in the file:/// context. By crafting a nested email attachment (message/rfc822) and setting its content type to application/pdf, Thunderbird may incorrectly render it as HTML when opened, allowing the embedded JavaScript to run without requiring a file download. This behavior relies on Thunderbird auto-saving the attachment to /tmp and linking to it via the file:/// protocol, potentially enabling JavaScript execution as part of the HTML. This vulnerability affects Thunderbird < 128.10.1 and Thunderbird < 138.0.1.
Weakness
The product’s user interface does not warn the user before undertaking an unsafe action on behalf of that user. This makes it easier for attackers to trick users into inflicting damage to their system.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Thunderbird | Mozilla | * | 128.10.1 (excluding) |
| Thunderbird | Mozilla | 129.0 (including) | 138.0.1 (excluding) |
| Red Hat Enterprise Linux 10 | RedHat | thunderbird-0:128.10.1-1.el10_0 | * |
| Red Hat Enterprise Linux 8 | RedHat | thunderbird-0:128.11.0-1.el8_10 | * |
| Red Hat Enterprise Linux 8.2 Advanced Update Support | RedHat | thunderbird-0:128.10.1-1.el8_2 | * |
| Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support | RedHat | thunderbird-0:128.10.1-1.el8_4 | * |
| Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support | RedHat | thunderbird-0:128.10.1-1.el8_6 | * |
| Red Hat Enterprise Linux 8.6 Telecommunications Update Service | RedHat | thunderbird-0:128.10.1-1.el8_6 | * |
| Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions | RedHat | thunderbird-0:128.10.1-1.el8_6 | * |
| Red Hat Enterprise Linux 8.8 Telecommunications Update Service | RedHat | thunderbird-0:128.10.1-1.el8_8 | * |
| Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions | RedHat | thunderbird-0:128.10.1-1.el8_8 | * |
| Red Hat Enterprise Linux 9 | RedHat | thunderbird-0:128.10.1-1.el9_6 | * |
| Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions | RedHat | thunderbird-0:128.10.1-1.el9_0 | * |
| Red Hat Enterprise Linux 9.2 Extended Update Support | RedHat | thunderbird-0:128.10.1-1.el9_2 | * |
| Red Hat Enterprise Linux 9.4 Extended Update Support | RedHat | thunderbird-0:128.10.1-1.el9_4 | * |
| Thunderbird | Ubuntu | focal | * |
| Thunderbird | Ubuntu | jammy | * |
| Thunderbird | Ubuntu | oracular | * |
| Thunderbird | Ubuntu | upstream | * |