CVE-2025-3909 is a high-severity vulnerability affecting Mozilla Thunderbird versions prior to 128.10.1 and 138.0.1. It allows for remote code execution via JavaScript by exploiting Thunderbird's handling of the X-Mozilla-External-Attachment-URL header and nested email attachments. An attacker can craft a malicious email with a specially formatted PDF attachment that, when opened, is incorrectly rendered as HTML, executing embedded JavaScript in the file:/// context. The CVSS score of 8.1 reflects a network-based attack with low complexity, requiring user interaction, and leading to high confidentiality and integrity impacts. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this vulnerability.
| Vendor | Product | Version(s) | CPE |
|---|---|---|---|
< 128.10.1CPE matchmatch criteria | cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* | ||
>= 129.0, < 138.0.1CPE matchmatch criteria | cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* |
CVSS version used by this source: 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
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No media coverage found for this CVE.
The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.