CVE-2026-16403 | Spoofing issue in the Address Bar component

Spoofing issue in the Address Bar component. This vulnerability was fixed in Firefox 153 and Thunderbird 153.

Published: 2026-07-21 Last update: 2026-07-22 Assigner: [email protected] Source: [email protected]
NVD Status：Undergoing Analysis，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-16403 is rated Low Risk (30.1/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.21%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-16403

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-07-23 0.13% 0.21% +0.08%
2 2026-07-22 — 0.13% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-16403

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-16403

GitHub Security Advisory for CVE-2026-16403

GHSA-33v9-jfq7-pmxc · Severity: medium — Spoofing issue in the Address Bar component. This vulnerability was fixed in Firefox 153.

OS Trackers for CVE-2026-16403

vendor priority summary link
debian not yet assigned CVE-2026-16403 not yet assigned priority: Debian including 1 source packages (firefox), 1 status rows across 1 suites (sid): open 1. https://security-tracker.debian.org/tracker/CVE-2026-16403

Affected software / configurations for CVE-2026-16403

Vendor Product Version Raw CPE
No affected products in dataset.

References for CVE-2026-16403

cvelogic Threat Intelligence