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Mozilla Firefox CVE-2026-16370

| EUVDEUVD-2026-46206 CRITICAL
Protection Mechanism Failure (CWE-693)
2026-07-21 mozilla GHSA-64m9-qg9m-54w5
Authentication Bypass Red Hat Mozilla
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 via web content with low complexity and no auth, but practical exploitation requires the victim to load a malicious page, so UI:R; high confidentiality/integrity impact, no availability effect.

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

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 22, 2026 - 17:23 vuln.today
CVSS changed
Jul 22, 2026 - 17:22 NVD
9.1 (CRITICAL)
CVE Published
Jul 21, 2026 - 12:37 cve.org
UNKNOWN (no severity yet)
CVE Published
Jul 21, 2026 - 12:37 cve.org
CRITICAL 9.1

DescriptionCVE.org

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

AnalysisAI

Protection-mechanism bypass in the DOM: Networking component of Mozilla Firefox lets a remote, unauthenticated attacker circumvent a browser security mitigation, exposing confidential data and enabling integrity compromise (CVSS 9.1) without user interaction. Reported by Mozilla and fixed in Firefox 153, the flaw affects users browsing to attacker-controlled web content. No public exploit identified at time of analysis, and the low EPSS score (0.15%) suggests exploitation is not yet widespread.

Technical ContextAI

The vulnerability lives in Firefox's DOM: Networking subsystem, which governs how web content initiates and processes network requests (fetch, XHR, WebSockets, CORS, and related same-origin/cross-origin controls). CWE-693 (Protection Mechanism Failure) indicates that an intended security control - likely an origin, CORS, or transport-security restriction enforced during DOM networking - can be bypassed rather than a memory-corruption bug. The affected CPE is cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* (all Firefox versions prior to the fix). The 'Authentication Bypass' tag and the networking context suggest the mitigation being defeated relates to cross-origin protections or credentialed request handling that normally shields one origin's data from another.

RemediationAI

Vendor-released patch: Firefox 153. Upgrade all Firefox installations to version 153 or later, which is the primary and complete fix; enterprises should also update the corresponding ESR channel build once available and validate via MFSA2026-68 (https://www.mozilla.org/security/advisories/mfsa2026-68/). Because Firefox auto-updates by default, most consumer installs will remediate automatically - confirm that managed/enterprise policies have not disabled automatic updates. No specific pre-patch workaround is documented; as compensating controls until updates roll out, restrict browsing to trusted sites via web filtering/proxy policy and consider network egress controls, accepting that these reduce but do not eliminate exposure to malicious web content. Bug details: https://bugzilla.mozilla.org/show_bug.cgi?id=1996495.

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Same weakness CWE-693 – Protection Mechanism Failure

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9.8
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CVE-2026-21510 HIGH POC
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Same technique Authentication Bypass

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CVE-2023-22515 CRITICAL POC
9.8
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CVE-2022-40684 CRITICAL POC
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CVE-2025-61882 CRITICAL POC
9.8
CVE-2024-0012 CRITICAL POC
9.3
CVE-2023-46805 HIGH POC
8.2

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-2026-16370 vulnerability details – vuln.today
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