CVE-2025-3523

Name: CVE-2025-3523
Creator: NVD / NIST
Published: 2025-04-15T15:16:09.957+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.4/10EPSS 0.26%

Last modified Jun 17, 2026

CVE-2025-3523 is a medium-severity vulnerability rated 6.4/10 on the CVSS scale. 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. EPSS estimates a 0.26% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

6.4/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:H/A:L

EPSS Probability

0.26%

17.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-451

Affected Software

Vendor	Product	Versions
Mozilla	Thunderbird	< 128.9.2
Mozilla	Thunderbird	>= 129.0, < 137.0.2

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1958385Permissions Required
https://www.mozilla.org/security/advisories/mfsa2025-26/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-27/Vendor Advisory

Timeline

Published: Apr 15, 2025
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2025-3523?

How severe is CVE-2025-3523?

CVE-2025-3523 has a CVSS score of 6.4/10 (MEDIUM severity). The EPSS model estimates a 0.26% probability of exploitation in the next 30 days.

How do I fix CVE-2025-3523?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2025-3523?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST