What is CVE-2025-54143?

CVE-2025-54143 is a critical-severity vulnerability in Mozilla Firefox, classified under Protection Mechanism Failure. CVSS score: 9.8/10. Published 2025-08-19.

How severe is CVE-2025-54143?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Vulnerability in Mozilla Firefox

CVE-2025-54143

Sandboxed iframes on webpages could potentially allow downloads to the device, bypassing the expected sandbox restrictions declared on the parent page. This vulnerability was fixed in Firefox for iOS 141.

EPSS: 0.005 (38.4th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Mozilla Firefox
Mozilla Firefox For Ios — versions 141

Weakness classification (CWE)

CWE-693 — Protection Mechanism Failure

References

security@mozilla.org (Permissions Required, Issue Tracking)
security@mozilla.org (Vendor Advisory)

Frequently asked questions

What is CVE-2025-54143?: CVE-2025-54143 is a critical-severity vulnerability in Mozilla Firefox, classified under Protection Mechanism Failure. CVSS score: 9.8/10. Published 2025-08-19.
How severe is CVE-2025-54143?: Critical severity. CVSS v3 base score is 9.8 out of 10.