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Mozilla Firefox EUVDEUVD-2026-37090

| CVE-2026-12299 MEDIUM
Access of Resource Using Incompatible Type (Type Confusion) (CWE-843)
2026-06-16 mozilla GHSA-4885-5pch-3x6m
Mozilla Memory Corruption Information Disclosure
Medium
Disputed · 5.4 Vendor: mozilla
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Severity by source

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

Network-delivered browser exploit requires active user page visit (UI:R); type confusion yields limited memory read/write (C:L/I:L) without scope change or availability impact.

3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
4.0 AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
SUSE
CRITICAL
qualitative
Red Hat
7.5 HIGH
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:L/I:L/A:N
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

Lifecycle Timeline

3
Analysis Generated
Jun 16, 2026 - 15:52 vuln.today
CVSS changed
Jun 16, 2026 - 15:22 NVD
5.4 (MEDIUM)
CVE Published
Jun 16, 2026 - 11:52 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

JIT miscompilation in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, and Firefox ESR 115.37.

AnalysisAI

JIT miscompilation in Mozilla Firefox's DOM Core & HTML component enables memory corruption and limited information disclosure when a user visits a malicious web page. Affecting Firefox prior to 152, Firefox ESR 140.x prior to 140.12, and Firefox ESR 115.x prior to 115.37, the root cause is a type confusion (CWE-843) in the Just-In-Time compiler that mishandles type information during DOM object operations. No public exploit has been identified and CISA's SSVC rates exploitation as none with partial technical impact; vendor patches are confirmed across all three release channels.

Technical ContextAI

The vulnerability resides in Mozilla Firefox's JIT (Just-In-Time) compiler as it processes operations within the DOM Core and HTML component. CWE-843 (Access of Resource Using Incompatible Type - commonly called type confusion) describes the root cause: the JIT compiler emits native machine code that accesses DOM-related memory regions using an incorrect or incompatible type, violating the runtime's type safety guarantees. JIT compilers accelerate JavaScript execution by converting hot code paths to native instructions at runtime; a miscompilation means the generated code may read or write memory assuming an object is one type when it is actually another, producing undefined behavior that can surface as memory corruption or unintended data disclosure. The affected CPE is cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* covering all standard and ESR Firefox releases. Three separate Mozilla security advisories were issued - mfsa2026-57, mfsa2026-58, and mfsa2026-59 - corresponding to the Firefox standard release, the ESR 140.x branch, and the ESR 115.x branch respectively, each documenting the same underlying flaw addressed at different version baselines.

RemediationAI

Upgrade to Firefox 152 or later for standard release users. Firefox ESR 140.x deployments should update to 140.12 or later, and Firefox ESR 115.x deployments should update to 115.37 or later - these are the confirmed fix versions per the CVE description and Mozilla advisories at https://www.mozilla.org/security/advisories/mfsa2026-57/, https://www.mozilla.org/security/advisories/mfsa2026-58/, and https://www.mozilla.org/security/advisories/mfsa2026-59/. No documented workaround is available in the referenced advisories. As a compensating control where immediate patching is not feasible, organizations may restrict outbound web traffic to a known-good allowlist via proxy filtering, though this significantly limits browsing capability. Disabling JavaScript execution entirely would prevent JIT compilation and thus the miscompilation trigger, but this breaks virtually all modern web applications and is operationally impractical in most environments.

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Same weakness CWE-843 – Access of Resource Using Incompatible Type (Type Confusion)

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Same technique Memory Corruption

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CVE-2015-5119 CRITICAL POC
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CVE-2011-2462 CRITICAL POC
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CVE-2011-0611 HIGH POC
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CVE-2014-0322 HIGH POC
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CVE-2012-1889 HIGH POC
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CVE-2012-4792 HIGH POC
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CVE-2010-3333 HIGH POC
7.8

Vendor StatusVendor

SUSE

Severity: Critical
Product Status
openSUSE Tumbleweed Fixed
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

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EUVD-2026-37090 vulnerability details – vuln.today
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