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Mozilla Firefox EUVDEUVD-2026-46218

| CVE-2026-16381 CRITICAL
Origin Validation Error (CWE-346)
2026-07-21 mozilla GHSA-pp6f-jf25-x95p
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-reachable unauthenticated same-origin bypass with high confidentiality/integrity impact, but a browser bug realistically needs the victim to load malicious content, so UI:R rather than UI:N.

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 - 19:40 vuln.today
CVSS changed
Jul 22, 2026 - 18:22 NVD
9.1 (CRITICAL)
CVE Published
Jul 21, 2026 - 12:37 cve.org
CRITICAL 9.1
CVE Published
Jul 21, 2026 - 12:37 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

Same-origin policy bypass in the Networking: DNS component. This vulnerability was fixed in Firefox 153 and Firefox ESR 140.13.

AnalysisAI

Same-origin policy bypass in Mozilla Firefox's Networking DNS component allows remote attackers to circumvent origin isolation and read or manipulate data belonging to other web origins. Affects Firefox before 153 and Firefox ESR before 140.13, exploitable over the network without authentication or user interaction (CVSS 9.1). No public exploit identified at time of analysis; EPSS is low (0.16%, 6th percentile).

Technical ContextAI

The flaw resides in Firefox's DNS-handling portion of its networking stack, which participates in enforcing the browser's same-origin policy - the fundamental boundary that prevents content from one origin (scheme + host + port) from reading or interacting with another. The root cause is classified as CWE-346 (Origin Validation Error), meaning the browser incorrectly resolves or attributes an origin, likely through DNS resolution behavior (e.g., name-to-origin association, rebinding-style confusion, or cache handling), allowing content to be treated as if it belonged to a different, more-trusted origin. Affected code is Gecko's networking DNS module; per CPE cpe:2.3:a:mozilla:firefox, all Firefox builds prior to the fixed versions are in scope.

RemediationAI

Vendor-released patch: upgrade to Firefox 153 or Firefox ESR 140.13, which contain the fix. Standard-channel users should update to Firefox 153, and enterprises running the Extended Support Release should deploy ESR 140.13; both are available through Firefox's built-in updater and enterprise deployment packages. Consult Mozilla advisories MFSA2026-68 (https://www.mozilla.org/security/advisories/mfsa2026-68/) and MFSA2026-70 (https://www.mozilla.org/security/advisories/mfsa2026-70/) to confirm the affected build and rollout. If immediate patching is not possible, reduce exposure by restricting browsing to trusted sites, enforcing enterprise policies that limit untrusted web content, and expediting the managed update - there is no documented per-feature toggle for the affected DNS/origin code, so upgrading is the only reliable fix.

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Same weakness CWE-346 – Origin Validation Error

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CVE-2023-29728 CRITICAL POC
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Same technique Authentication Bypass

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CVE-2013-2465 CRITICAL POC
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CVE-2011-3544 CRITICAL POC
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CVE-2022-40684 CRITICAL POC
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CVE-2025-61882 CRITICAL POC
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CVE-2024-0012 CRITICAL POC
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CVE-2023-46805 HIGH POC
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Vendor StatusVendor

SUSE

Severity: Critical
Product Status
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS Affected
SUSE Linux Enterprise Module for Desktop Applications 15 SP7 Affected

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EUVD-2026-46218 vulnerability details – vuln.today
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