What is CVE-2026-13356?

CVE-2026-13356 is a medium-severity vulnerability in Mozilla Firefox, classified under User Interface (UI) Misrepresentation of Critical Information. CVSS score: 6.3/10. Published 2026-07-07.

How severe is CVE-2026-13356?

Medium severity. CVSS v3 base score is 6.3 out of 10.

Vulnerability in Mozilla Firefox

CVE-2026-13356

A malicious webpage could interrupt a pending navigation by enqueuing a synchronous JavaScript dialog, causing the browser UI to display the destination origin in the address bar while continuing to render attacker-controlled content. This vulnerability was fixed in Firefox for iOS 152.3.

EPSS: 0.001 (3.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L.

Affected products

Mozilla Firefox
Mozilla Firefox For Ios — versions 152.3

Weakness classification (CWE)

CWE-451 — User Interface (UI) Misrepresentation of Critical Information

References

security@mozilla.org (Permissions Required)
security@mozilla.org (Vendor Advisory)

Frequently asked questions

What is CVE-2026-13356?: CVE-2026-13356 is a medium-severity vulnerability in Mozilla Firefox, classified under User Interface (UI) Misrepresentation of Critical Information. CVSS score: 6.3/10. Published 2026-07-07.
How severe is CVE-2026-13356?: Medium severity. CVSS v3 base score is 6.3 out of 10.