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Mozilla Firefox CVE-2026-16403

| EUVDEUVD-2026-46241 MEDIUM
User Interface (UI) Misrepresentation of Critical Information (CWE-451)
2026-07-21 mozilla GHSA-33v9-jfq7-pmxc
Information Disclosure Red Hat Mozilla
Medium
Disputed · 6.5 Vendor: mozilla
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Severity by source

Sources disagree (Low–Critical)
Vendor (mozilla) PRIMARY
6.5 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
vuln.today AI
6.5 MEDIUM

Network-delivered spoofing requires only passive user navigation (UI:R, PR:N); integrity is fully compromised by the false origin display while confidentiality and availability are unaffected.

3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
4.0 AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
SUSE
CRITICAL
qualitative
Red Hat
3.4 LOW
qualitative

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorVendor: mozilla

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

Lifecycle Timeline

4
Analysis Generated
Jul 22, 2026 - 19:08 vuln.today
CVSS changed
Jul 22, 2026 - 18:22 NVD
6.5 (MEDIUM)
CVE Published
Jul 21, 2026 - 12:38 cve.org
UNKNOWN (no severity yet)
CVE Published
Jul 21, 2026 - 12:38 cve.org
MEDIUM 6.5

DescriptionCVE.org

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

AnalysisAI

Address bar spoofing in Mozilla Firefox (all versions prior to 153) enables a remote, unauthenticated attacker to misrepresent the displayed origin in the browser's address bar, the primary trust signal users rely on to validate site authenticity. The CVSS vector (AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N) confirms exploitation is low-complexity and requires only a single user interaction - navigating to a crafted page - with no authentication or special privileges needed from the attacker. No public exploit has been identified and EPSS sits at 0.13% (3rd percentile), indicating limited exploitation activity; however, the integrity of user trust decisions is fully undermined when the flaw is triggered, making it an effective phishing enabler.

Technical ContextAI

CWE-451 (User Interface Misrepresentation of Critical Information) identifies the root cause: Firefox's Address Bar component fails to correctly represent the true origin of content being rendered, allowing a manipulated or transitional browser state to persist a misleading URL. The browser address bar is the foundational trust anchor of web security - all certificate validation, same-origin policy reasoning, and user decision-making about credential entry rely on it. CPE data (cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*) indicates all Firefox releases across all platforms are affected prior to the patch. The exact spoofing mechanism - whether via navigation racing, history manipulation, or a rendering artifact - is not publicly disclosed; the Bugzilla issue (1972244) is likely still access-restricted, which is common practice for browser address bar spoofing bugs to delay weaponization.

RemediationAI

Upgrade Mozilla Firefox to version 153 or later, which contains the vendor-released patch as confirmed by Mozilla Security Advisory MFSA2026-68 (https://www.mozilla.org/security/advisories/mfsa2026-68/). Most Firefox installations on supported platforms will receive this update automatically via the built-in updater; verify the installed version via Help > About Firefox. For enterprise environments managing Firefox deployments via policy, prioritize distribution of version 153 through your endpoint management tooling. No standalone workaround exists that fully mitigates address bar spoofing without upgrading, as it is a rendering-layer defect. As an interim compensating control, organizations can deploy browser isolation solutions or enforce strict Content Security Policy headers on internal applications - these do not prevent the spoofing itself but reduce the blast radius of phishing enabled by it. Users in high-risk environments (finance, healthcare) should be briefed to independently verify SSL certificate details via the padlock/site info UI rather than relying solely on the address bar until patched.

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Vendor StatusVendor

SUSE

Severity: Critical
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected
SUSE Linux Enterprise Module for Desktop Applications 15 SP7 Affected
SUSE Linux Enterprise Module for Package Hub 15 SP7 Affected

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CVE-2026-16403 vulnerability details – vuln.today
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