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Mozilla Firefox CVE-2026-16396

| EUVDEUVD-2026-46234 HIGH
Improper Privilege Management (CWE-269)
2026-07-21 mozilla GHSA-97fr-g29v-hhwf
Mozilla Privilege Escalation Red Hat
High
Disputed · 8.8 Vendor: mozilla
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Severity by source

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

A WebExtension must be installed/loaded to reach the flaw, implying user interaction and extension-level privileges (UI:R, PR:L), while the escalation yields full high impact on the browser (C/I/A:H).

3.1 AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:H/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:R/S:U/C:H/I:H/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

7
Re-analysis Queued
Jul 24, 2026 - 21:22 vuln.today
cvss_changed
Severity Changed
Jul 24, 2026 - 21:22 NVD
CRITICAL HIGH
CVSS changed
Jul 24, 2026 - 21:22 NVD
9.8 (CRITICAL) 8.8 (HIGH)
Analysis Generated
Jul 22, 2026 - 21:12 vuln.today
CVSS changed
Jul 22, 2026 - 19:22 NVD
9.8 (CRITICAL)
CVE Published
Jul 21, 2026 - 12:38 cve.org
CRITICAL 9.8
CVE Published
Jul 21, 2026 - 12:38 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

Privilege escalation in WebExtensions. This vulnerability was fixed in Firefox 153 and Firefox ESR 140.13.

AnalysisAI

Privilege escalation in the WebExtensions subsystem of Mozilla Firefox lets a WebExtension gain capabilities beyond its granted permission set, corresponding to CWE-269 (Improper Privilege Management). Mozilla, the reporting vendor, fixed the issue in Firefox 153 and Firefox ESR 140.13 (advisories MFSA2026-68/70/71/72). No public exploit has been identified at time of analysis and the EPSS probability is low at 0.14% (4th percentile), despite the vendor-supplied 9.8 CVSS score.

Technical ContextAI

WebExtensions is Firefox's cross-browser extension framework, which runs add-ons in a privilege-scoped model where each extension is granted only the host permissions and APIs declared in its manifest and approved by the user. A CWE-269 Improper Privilege Management flaw in this layer means the boundary that confines an extension to its declared privileges can be crossed, allowing extension code (or content interacting with it) to obtain higher-privileged browser capabilities than intended. The affected CPE is cpe:2.3:a:mozilla:firefox (versions prior to the fix), and because Firefox ESR 140.13 is separately patched, the ESR 140.x line is confirmed affected alongside the mainline release channel.

RemediationAI

Vendor-released patch: upgrade to Firefox 153 on the release channel, or to Firefox ESR 140.13 for organizations on the Extended Support Release train; these are the exact fixed versions cited by Mozilla in advisories MFSA2026-68/70/71/72 (see https://www.mozilla.org/security/advisories/mfsa2026-71/). Because the root cause is in the WebExtensions privilege model, the most effective compensating control until patched is to tighten extension governance: restrict installation to admin-approved add-ons via the ExtensionSettings enterprise policy (install_sources plus allowed/blocked lists) and remove untrusted extensions, accepting that this reduces user flexibility. Enabling automatic updates ensures the patched build is delivered promptly, and enterprise deployments can push the fixed version through their standard update infrastructure.

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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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CVE-2026-16396 vulnerability details – vuln.today
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