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Mozilla Firefox EUVDEUVD-2026-37067

| CVE-2026-12321 MEDIUM
Always-Incorrect Control Flow Implementation (CWE-670)
2026-06-16 mozilla GHSA-r946-vv6g-44hh
Information Disclosure Mozilla
Medium
Disputed · 5.4 Vendor: mozilla
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Severity by source

Sources disagree (Low–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 via browser visit (AV:N), no attacker privileges needed (PR:N), user must actively visit page (UI:R), limited read/write within unchanged browser scope, no 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
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 VectorVendor: mozilla

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
Jul 23, 2026 - 16:40 vuln.today
CVE Published
Jun 16, 2026 - 11:52 cve.org
UNKNOWN (no severity yet)
CVE Published
Jun 16, 2026 - 11:52 cve.org
MEDIUM 5.4

DescriptionCVE.org

JIT miscompilation in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 152.

AnalysisAI

JIT miscompilation in Mozilla Firefox's WebAssembly component (all versions prior to Firefox 152) exposes users to partial confidentiality and integrity compromise when visiting attacker-controlled web content. The flaw stems from incorrect control flow implementation (CWE-670) in the JIT compiler when processing crafted WebAssembly bytecode, resulting in erroneous native code generation that can allow limited memory reads or unintended writes. No active exploitation is confirmed - the vulnerability is absent from CISA KEV, EPSS is at the 5th percentile (0.16%), and SSVC marks exploitation as 'none' - placing this firmly in routine patch priority despite its network-accessible attack vector. Mozilla has released a fix in Firefox 152 via advisories MFSA2026-57 and MFSA2026-60.

Technical ContextAI

CWE-670 (Always-Incorrect Control Flow Implementation) describes a flaw where a program's logic produces control flow that is structurally wrong - in this case within Firefox's Just-In-Time compiler for the WebAssembly (Wasm) subsystem. JIT compilers translate Wasm bytecode into native machine code at runtime to maximize performance; a miscompilation can corrupt type assumptions, violate memory safety invariants, or produce incorrect branching, all of which can be exploited to leak memory contents or alter program state. The affected product is Mozilla Firefox across all versions per CPE cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*, with no specified floor version in available data. The tags referencing Red Hat and SUSE indicate this vulnerability is also tracked and addressed through downstream Linux distribution security channels that ship Firefox packages.

RemediationAI

The primary fix is to upgrade Mozilla Firefox to version 152 or later, as confirmed by Mozilla in advisories MFSA2026-57 and MFSA2026-60 (https://www.mozilla.org/security/advisories/mfsa2026-57/, https://www.mozilla.org/security/advisories/mfsa2026-60/). Red Hat and SUSE users should apply updated Firefox packages through their respective distribution security errata channels. As an interim compensating control, WebAssembly can be disabled in Firefox via about:config by setting the preference javascript.options.wasm to false - this eliminates the JIT Wasm attack surface entirely but will break any website or web application relying on WebAssembly, which is a significant usability trade-off in modern browser environments. Organizations running managed Firefox deployments should treat this as a standard browser update rather than an emergency patch given the low EPSS and absent KEV listing.

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Vendor StatusVendor

SUSE

Severity: Critical
Product Status
openSUSE Tumbleweed Fixed
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

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EUVD-2026-37067 vulnerability details – vuln.today
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