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Mozilla Firefox CVE-2026-8960

| EUVDEUVD-2026-30909 HIGH
Authentication Bypass by Spoofing (CWE-290)
2026-05-19 mozilla GHSA-57v8-q85x-pwx6
Authentication Bypass Mozilla
High
Disputed · 7.5 NVD
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Severity by source

Sources disagree (Low–High)
NVD PRIMARY
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
vuln.today AI
6.5 MEDIUM

Network-reachable spoofing with no privileges, but as a CWE-290 deception it realistically needs the victim to view/interact (UI:R); impact is integrity-only, so C:N and A:N.

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
HIGH
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 VectorNVD

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

Lifecycle Timeline

3
Analysis Generated
Jul 23, 2026 - 17:41 vuln.today
CVE Published
May 19, 2026 - 12:29 nvd
UNKNOWN (no severity yet)
CVE Published
May 19, 2026 - 12:29 cve.org
HIGH 7.5

DescriptionCVE.org

Spoofing issue in WebExtensions. This vulnerability was fixed in Firefox 151.

AnalysisAI

Spoofing in Mozilla Firefox WebExtensions (versions prior to 151) allows remote attackers to misrepresent extension-controlled content or UI, undermining the integrity of what a user believes they are seeing or interacting with. The CVSS 3.1 vector (7.5) reflects a high integrity impact with no confidentiality or availability loss, and Mozilla has shipped a fix in Firefox 151. There is no public exploit identified at time of analysis, EPSS is very low (0.03%), and CISA SSVC records no known exploitation.

Technical ContextAI

The flaw sits in Firefox's WebExtensions subsystem - the API layer that browser add-ons use to interact with pages, UI surfaces, and browser internals. CWE-290 (Authentication Bypass by Spoofing) is the root-cause class: a component trusts an origin, identity, or UI element that can be forged, so an attacker can impersonate a trusted source without valid credentials. In practice a spoofing defect in WebExtensions typically means content or an extension surface can be made to appear as though it originates from a legitimate/trusted context, defeating the assurance a user or extension places in that indicator. The single affected CPE is cpe:2.3:a:mozilla:firefox (all versions up to the fix), and Mozilla tracked it internally as Bugzilla 1940116 and advisories MFSA2026-46 / MFSA2026-50.

RemediationAI

Vendor-released patch: Firefox 151 - upgrade all Firefox installations to 151 or later, which is the definitive fix. Organizations running distro-packaged Firefox should apply the corresponding SUSE and Red Hat security updates as they land rather than the upstream binary. Because Firefox auto-updates by default, ensure automatic updates are not disabled via enterprise policy; for managed fleets, push 151 through your update management/GPO/MDM channel. No specific pre-patch workaround is documented for this WebExtensions spoofing issue; a defensible compensating control until patching is to restrict or vet installed WebExtensions via enterprise extension policy (ExtensionSettings), accepting the trade-off that this may block extensions users rely on. Reference the Mozilla advisories https://www.mozilla.org/security/advisories/mfsa2026-46/ and https://www.mozilla.org/security/advisories/mfsa2026-50/ for the definitive fixed build.

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Same weakness CWE-290 – Authentication Bypass by Spoofing

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9.8
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6.5
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9.8
CVE-2023-51350 CRITICAL POC
9.8
CVE-2022-3180 CRITICAL
9.8
CVE-2025-66570 CRITICAL POC
10.0
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Same technique Authentication Bypass

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CVE-2023-22515 CRITICAL POC
9.8
CVE-2012-4681 CRITICAL POC
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CVE-2013-2465 CRITICAL POC
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CVE-2011-3544 CRITICAL POC
9.8
CVE-2022-40684 CRITICAL POC
9.8
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: High
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed
SUSE Linux Enterprise Module for Desktop Applications 15 SP7 Fixed
SUSE Linux Enterprise Module for Package Hub 15 SP7 Fixed

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CVE-2026-8960 vulnerability details – vuln.today
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