CVE-2025-6435
Published: 24 June 2025
Summary
CVE-2025-6435 is a high-severity Unrestricted Upload of File with Dangerous Type (CWE-434) vulnerability in Mozilla Firefox. Its CVSS base score is 8.1 (High).
Operationally, ranked in the top 33.3% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-19016
Vulnerability details
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…
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a malicious executable. This vulnerability was fixed in Firefox 140 and Thunderbird 140.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Requiring identifiable owners for portable devices reduces the attack surface for unrestricted uploads of dangerous file types via anonymous media.
Dangerous file uploads can be detonated in the chamber to determine malice before any production write or execution occurs.
Prevents unrestricted writing of arbitrary or malicious firmware by keeping hardware write-protect enabled except under tightly controlled manual procedures.
Scans files from external sources on download/open/execute, blocking unrestricted uploads of dangerous file types.