CVE-2025-4086: firefox — Fix

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.

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CVSS v3.1 Score

6.5

MEDIUM

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

Weakness Type (CWE)

CWE-451 CWE-451

Affected Products

Vendor	Product	Versions
mozilla	firefox	< 138.0
mozilla	thunderbird	< 138.0

References

Advisories & Patches

https://www.mozilla.org/security/advisories/mfsa2025-28/ https://www.mozilla.org/security/advisories/mfsa2025-31/

Other References

https://bugzilla.mozilla.org/show_bug.cgi?id=1945705

Frequently Asked Questions

What is CVE-2025-4086? +

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. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2025-4086? +

CVE-2025-4086 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-4086? +

CVE-2025-4086 affects products from mozilla, specifically: firefox, thunderbird. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-4086? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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