CVE-2025-4086

Name: CVE-2025-4086
Creator: NVD / NIST
Published: 2025-04-29T14:15:35.267+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 0.24%

Last modified Jun 17, 2026

CVE-2025-4086 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. A specially crafted filename containing a large number of encoded newline characters could obscure the file's extension when displayed in the download dialog. *This bug only affects Thunderbird for Android. Other versions of Thunderbird are unaffected.*. EPSS estimates a 0.24% chance of exploitation in the next 30 days.

Description

A specially crafted filename containing a large number of encoded newline characters could obscure the file's extension when displayed in the download dialog. *This bug only affects Thunderbird for Android. Other versions of Thunderbird are unaffected.*. This vulnerability was fixed in Firefox 138 and Thunderbird 138.

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

0.24%

14.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-451

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 138.0
Mozilla	Thunderbird	< 138.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1945705Permissions Required
https://www.mozilla.org/security/advisories/mfsa2025-28/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-31/Vendor Advisory

Timeline

Published: Apr 29, 2025
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2025-4086?

How severe is CVE-2025-4086?

CVE-2025-4086 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.24% probability of exploitation in the next 30 days.

How do I fix CVE-2025-4086?

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-2025-4086?

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

Scan your code now

Source: NVD / NIST