What is CVE-2025-55031?

CVE-2025-55031 is a critical-severity vulnerability in Mozilla Firefox, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 9.8/10. Published 2025-08-19.

How severe is CVE-2025-55031?

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

Open Redirect in Mozilla Firefox

CVE-2025-55031

Malicious pages could use Firefox for iOS to pass FIDO: links to the OS and trigger the hybrid passkey transport. An attacker within Bluetooth range could have used this to trick the user into using their passkey to log the attacker's computer into the target account. This vulnerability was fixed in Firefox for iOS 142 and Focus for iOS 142.

Vulnerability class: Open Redirect

Published 2025-08-19 · last modified 2026-09-30.

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.

EPSS exploit prediction

EPSS: 0.004 (36.0th percentile), scored 2026-10-20.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 36th percentile — 36.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: +0.000

Affected products

Weakness classification (CWE)

CWE-601 — URL Redirection to Untrusted Site (Open Redirect)

References

bugzilla.mozilla.org/show_bug.cgi (Permissions Required, Issue Tracking)
bugzilla.mozilla.org/show_bug.cgi (Permissions Required, Issue Tracking)
www.mozilla.org/security/advisories/mfsa2025-68/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2025-69/ (Vendor Advisory)

Frequently asked questions

What is CVE-2025-55031?: CVE-2025-55031 is a critical-severity vulnerability in Mozilla Firefox, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 9.8/10. Published 2025-08-19.
How severe is CVE-2025-55031?: Critical severity. CVSS v3 base score is 9.8 out of 10.