CVE-2025-6435

Name: CVE-2025-6435
Creator: NVD / NIST
Published: 2025-06-24T13:15:24.56+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.1/10EPSS 0.38%

Last modified Jun 17, 2026

CVE-2025-6435 is a high-severity vulnerability rated 8.1/10 on the CVSS scale. If a user saved a response from the Network tab in Devtools using the Save As context menu option, that file may not have been saved with the `.download` file extension. This could have led to the user inadvertently running a malicious executable. EPSS estimates a 0.38% chance of exploitation in the next 30 days.

Description

If a user saved a response from the Network tab in Devtools using the Save As context menu option, that file may not have been saved with the `.download` file extension. This could have led to the user inadvertently running a malicious executable. This vulnerability was fixed in Firefox 140 and Thunderbird 140.

Metrics

CVSS 3.1

8.1/10

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

EPSS Probability

0.38%

29.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-434

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 140.0
Mozilla	Thunderbird	< 140.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1950056Permissions Required
https://bugzilla.mozilla.org/show_bug.cgi?id=1961777Permissions Required
https://www.mozilla.org/security/advisories/mfsa2025-51/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2025-54/Vendor Advisory

Timeline

Published: Jun 24, 2025
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2025-6435?

How severe is CVE-2025-6435?

CVE-2025-6435 has a CVSS score of 8.1/10 (HIGH severity). The EPSS model estimates a 0.38% probability of exploitation in the next 30 days.

How do I fix CVE-2025-6435?

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-2025-6435?

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

Scan your code now

Source: NVD / NIST