What is CVE-2025-3859?

CVE-2025-3859 is a medium-severity vulnerability in Mozilla Firefox_focus, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2025-04-30.

How severe is CVE-2025-3859?

Medium severity. CVSS v3 base score is 6.1 out of 10.

Open Redirect in Mozilla Firefox_focus

CVE-2025-3859

Websites directing users to long URLs that caused eliding to occur in the location view could leverage the truncating behavior to potentially trick users into thinking they were on a different webpage. This vulnerability was fixed in Focus…

Vulnerability class: Open Redirect

EPSS: 0.002 (6.8th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

Affected products

Mozilla Firefox_focus
Mozilla Focus — versions 138

Weakness classification (CWE)

References

security@mozilla.org (Issue Tracking)
security@mozilla.org (Vendor Advisory)

Frequently asked questions

What is CVE-2025-3859?: CVE-2025-3859 is a medium-severity vulnerability in Mozilla Firefox_focus, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2025-04-30.
How severe is CVE-2025-3859?: Medium severity. CVSS v3 base score is 6.1 out of 10.