CVE-2025-3909

HIGH EPSS 28.2%
Published May 14, 20251y ago · Modified Jun 17, 20261w ago
8.1 CVSS 3.1
High
Find Similar
Published May 14, 2025 1y ago
Last Modified Jun 17, 2026 1w ago

Description

Thunderbird's 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 was fixed in Thunderbird 128.10.1 and Thunderbird 138.0.1.

CVSS Details

Base Score
8.1
Exploitability
2.8
Impact
5.2
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction Required
Scope Unchanged
Confidentiality High
Integrity High
Availability None

Threat Intelligence

EPSS Exploit Probability
28.2% percentile
Exploit & Patch Status
No Known Exploit
No Patch Available

Weaknesses 1

CWE-356

Affected Products 2

VendorProductVersionRange
mozillathunderbird* <128.10.1
mozillathunderbird*≥129.0  –  <138.0.1

References 4

  • bugzilla.mozilla.org https://bugzilla.mozilla.org/show_bug.cgi?id=1958376
    Permissions Required
  • lists.debian.org https://lists.debian.org/debian-lts-announce/2025/05/msg00022.html
  • mozilla.org https://www.mozilla.org/security/advisories/mfsa2025-34/
    Vendor Advisory
  • mozilla.org https://www.mozilla.org/security/advisories/mfsa2025-35/
    Vendor Advisory

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.