What is CVE-2025-3523?

CVE-2025-3523 is a medium-severity vulnerability in Mozilla Thunderbird, classified under User Interface (UI) Misrepresentation of Critical Information. CVSS score: 6.4/10. Published 2025-04-15.

How severe is CVE-2025-3523?

Medium severity. CVSS v3 base score is 6.4 out of 10.

Is CVE-2025-3523 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Mozilla Thunderbird

CVE-2025-3523

When an email contains multiple attachments with external links via the X-Mozilla-External-Attachment-URL header, only the last link is shown when hovering over any attachment. Although the correct link is used on click, the misleading hover text could trick users into downloading content from untrusted sources. This vulnerability was fixed in Thunderbird 137.0.2 and Thunderbird 128.9.2.

EPSS: 0.003 (22.4th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.4 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:H/A:L.

Affected products

Mozilla Thunderbird — versions 128.9.2, 137.0.2

Weakness classification (CWE)

CWE-451 — User Interface (UI) Misrepresentation of Critical Information

Public proof-of-concept exploits

w4zu/Debian_

References

security@mozilla.org (Permissions Required)
security@mozilla.org (Vendor Advisory)
security@mozilla.org (Vendor Advisory)

Frequently asked questions

What is CVE-2025-3523?: CVE-2025-3523 is a medium-severity vulnerability in Mozilla Thunderbird, classified under User Interface (UI) Misrepresentation of Critical Information. CVSS score: 6.4/10. Published 2025-04-15.
How severe is CVE-2025-3523?: Medium severity. CVSS v3 base score is 6.4 out of 10.
Is CVE-2025-3523 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.