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Mozilla Firefox CVE-2026-16394

| EUVDEUVD-2026-46232 CRITICAL
Protection Mechanism Failure (CWE-693)
2026-07-21 mozilla GHSA-qvxh-vvjm-vpwg
Authentication Bypass Mozilla Suse Red Hat
Critical
Disputed · 9.1 Vendor: mozilla
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Severity by source

Sources disagree (Medium–Critical)
Vendor (mozilla) PRIMARY
9.1 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
vuln.today AI
8.1 HIGH

Network-delivered web content with no auth (AV:N/PR:N), but a client-side browser bug realistically needs the victim to load a page, so UI:R; high C/I, no availability impact.

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

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

Lifecycle Timeline

4
Analysis Generated
Jul 21, 2026 - 20:23 vuln.today
CVSS changed
Jul 21, 2026 - 20:22 NVD
9.1 (CRITICAL)
CVE Published
Jul 21, 2026 - 12:38 cve.org
UNKNOWN (no severity yet)
CVE Published
Jul 21, 2026 - 12:38 cve.org
CRITICAL 9.1

DescriptionCVE.org

Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 153.

Articles & Coverage 1

News Critical DOM Security Bypass in Mozilla Firefox - CVE-2026-16394 Jul 21, 2026

AnalysisAI

Protection mechanism failure in the DOM: Security component of Mozilla Firefox lets remote attackers bypass a browser security mitigation, undermining defenses that isolate web content and enforce origin/policy boundaries. Mozilla rates this Critical (CVSS 9.1) with high confidentiality and integrity impact and no authentication or user interaction required per the assigned vector; it is corrected in Firefox 153 (MFSA 2026-68). …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Lure victim to malicious page
Delivery
Serve crafted DOM/script content
Exploit
Bypass DOM security mitigation
Execution
Access cross-origin data or subvert policy
Impact
Compromise confidentiality and integrity of session
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Vulnerability AssessmentAI

Exploitation Exploitation requires the victim to load attacker-controlled or attacker-influenced web content in a vulnerable Firefox (pre-153) instance, since the vulnerable code is the client-side DOM: Security enforcement layer; the CVSS vector states no privileges and no user interaction (PR:N/UI:N), but realistically the user must navigate to or render malicious content, which is the practical limiting factor. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The Mozilla-supplied CVSS vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N, 9.1 Critical) presents a network-reachable, unauthenticated, no-interaction, high-impact bug - which is severe on paper. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker hosts a malicious web page (or injects content into a site the victim visits) that exercises the DOM: Security bypass to escape a browser mitigation, allowing script to access data or perform actions the security control should have blocked. Combined with another primitive, this could expose cross-origin data or subvert page integrity in the victim's session. …
Remediation Vendor-released patch: Firefox 153 - upgrade all Firefox installations to 153 or later, which is the primary and complete fix per MFSA 2026-68 (https://www.mozilla.org/security/advisories/mfsa2026-68/). … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours: identify all Firefox instances across the organization and stage Firefox 153 (MFSA 2026-68) in your patch management system; test in non-production environments to confirm compatibility with critical business applications. …

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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-2026-16394 vulnerability details – vuln.today
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