Is CVE-2025-4086 in the CISA KEV catalog?

No. CVE-2025-4086 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2025-4086?

CVE-2025-4086 has a CVSS v3 base score of 6.5 (MEDIUM).

What is the EPSS score for CVE-2025-4086?

CVE-2025-4086 has an EPSS score of 0.24% (15th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2025-4086?

Upgrade DeveloperEdition to 138.0 or later. Fixes are available for 3 affected products.

CVE & CISA-KEV Catalog

CVE-2025-4086

MEDIUM

6.5

CVSS v3

NVD

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.

CWE-451

How to fix

Remediation Available

DeveloperEditionWindows application

Affected:138.0Fixed in:138.0Mozilla

Mozilla Firefox (en-US)Windows application

Affected:138.0Fixed in:138.0Mozilla

Mozilla Thunderbird (en-US)Windows application

Affected:138.0Fixed in:138.0Mozilla

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityLow

AvailabilityNone

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

Exploit Intelligence

0.24%probability of exploitation in 30 days

15thpercentile

Low risk: more likely to be exploited than 15% of all known CVEs.

References

Vendor Advisory2

Other references1

bugzilla.mozilla.org

Related Vulnerabilities

Other CWE-451 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2024-38112	High	7.5	84%	KEV	Fix
CVE-2025-9491	High	7.8	63%	-	-
CVE-2024-43461	High	8.8	52%	KEV	Fix
CVE-2024-38197	Medium	6.5	16%	-	-
CVE-2026-21527	High	6.5	9.5%	-	Fix
CVE-2024-49040	High	7.5	7.7%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-13.