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Red Hat EUVDEUVD-2026-14848

| CVE-2026-4716 CRITICAL
Use of Uninitialized Resource (CWE-908)
2026-03-24 mozilla
Information Disclosure Red Hat Mozilla Suse
Critical
Disputed · 9.1 NVD
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Craft malicious JavaScript payload
  2. Exploit
    Trigger uninitialized memory access in Firefox JavaScript Engine
  3. Execution
    Read sensitive data from memory
  4. Impact
    Cause denial of service crash

Vulnerability Assessment

Weakness
CWE
CWE-908
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
ASVS 5.0
V15 - Secure Coding and Architecture Variable initialization
Exploitation Conditions

Remote unauthenticated attacker can exploit via malicious JavaScript code executed in Firefox < 149 or Firefox ESR < 140.9. Victim must visit attacker-controlled website or open malicious HTML file in vulnerable Firefox browser. No user interaction required beyond normal browsing.
Impact

Without published CVSS or EPSS scores, risk assessment relies on available context signals. The vulnerability is tagged as Information Disclosure rather than Code Execution, suggesting limited immediate remote code execution risk but meaningful confidentiality impact. No CVSS vector data is available to assess attack complexity, privileges required, or scope; however, JavaScript Engine vulnerabilities are typically network-accessible (attack vector: network) and may require minimal or no user interaction in certain scenarios (e.g., malicious web content). The existence of two Mozilla security advisories (MFSA2026-20 and MFSA2026-22) indicates this received formal security review and coordinated disclosure. KEV status and active exploitation data are not provided, so assume this follows standard Mozilla vulnerability timelines with patches available at release. Real-world priority is moderate to high: memory disclosure from a JavaScript engine is concerning in a browser context where sandboxing may limit impact, but information leakage can facilitate secondary attacks.
Exploit ScenarioDerived

An attacker crafts a malicious webpage containing specially crafted JavaScript code designed to trigger uninitialized memory reads or out-of-bounds access in the JavaScript Engine. When a vulnerable Firefox user visits this page, the JavaScript executes within the browser context and leaks sensitive memory contents—such as encryption keys, session tokens, or data from other browser tabs—which the attacker exfiltrates via JavaScript side-channel techniques (e.g., timing attacks or direct HTTP requests). The attack requires the user to visit an attacker-controlled or compromised website, making it a realistic threat for drive-by exploitation.
Act Now Prioritize within 24-48h. Why: CRITICAL severity.
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 24, 2026

Mozilla Firefox versions below 149 and Firefox ESR below 140.9 contain memory safety flaws in the JavaScript Engine that enable remote code execution and denial of service attacks without user interaction or special privileges. An unauthenticated attacker can exploit improper boundary condition handling and uninitialized memory to achieve high-impact confidentiality violations and system availability disruption. No patch is currently available.

Earlier versions of this analysis (1)
v1 Mar 24, 2026 - 12:45 CVSS 9.1

A memory safety vulnerability exists in the Firefox JavaScript Engine due to incorrect boundary conditions and uninitialized memory handling, potentially allowing information disclosure to attackers. Firefox versions below 149 and Firefox ESR versions below 140.9 are affected. An attacker could exploit this flaw to leak sensitive information from process memory, though the exact attack vector and exploitability status require analysis of the referenced Mozilla security advisories.

RemediationAI

Users should immediately update Firefox to version 149 or later, and Firefox ESR users should upgrade to version 140.9 or later. Both updates are available through the official Mozilla website and automatic update mechanisms within the browser. Until patching can be deployed, users should disable JavaScript in the browser settings if feasible for their workflow, though this severely limits functionality. System administrators can enforce updates via group policy (Windows) or configuration management tools, and should prioritize rollout given the information disclosure risk. Refer to the complete remediation guidance in Mozilla's official advisories at https://www.mozilla.org/security/advisories/mfsa2026-20/ and https://www.mozilla.org/security/advisories/mfsa2026-22/.

Affected VersionsENISA

Firefox ESR unspecified <140.9
Firefox unspecified <149

Affected Packages

euvd firefox_esr_unspecified fix: 140.9
euvd firefox_unspecified fix: 149

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 2 packages in euvd

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Technical ContextAI · show details

The vulnerability resides in Mozilla Firefox's JavaScript Engine (SpiderMonkey), a core component responsible for parsing, compiling, and executing JavaScript code. The root cause involves improper boundary condition checks combined with uninitialized memory access patterns, classified under CWE categories related to memory safety (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer, or similar). The affected products span both the mainline Firefox release (cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*) and the extended support release track (cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*), indicating this is a critical component affecting millions of browser instances. Improper handling of memory boundaries in a JIT-compiled or interpreted JavaScript context could allow out-of-bounds reads to access adjacent memory regions containing sensitive data.

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

Sources disagree (Medium–Critical)
NVD PRIMARY 9.1 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
SUSE CRITICAL
Red Hat 6.1 MEDIUM

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
High
Integrity
None
Availability
High

Lifecycle Timeline

2
Patch released
Mar 31, 2026 - 21:13 nvd
Patch available
CVE Published
Mar 24, 2026 - 12:30 nvd
CRITICAL 9.1

DescriptionCVE.org

Incorrect boundary conditions, uninitialized memory in the JavaScript Engine component. This vulnerability affects Firefox < 149 and Firefox ESR < 140.9.

Executive ViewAI

Why It Matters

Organizations using the JavaScript Engine component. This vulnerability affects Firefox face critical risk from CVE-2026-4716 rated CVSS 9.1. Successful exploitation could critically impact the confidentiality, integrity, and availability of affected systems. Organizations should apply vendor updates immediately when available and implement compensating controls in the interim.

Business Impact: Severe
Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Implement network-level access controls to limit exposure; (2) Enable enhanced monitoring and alerting; (3) Apply principle of least privilege.

Threat Intelligence Overview

EPSS Score
0.0%
Top 96% exploitable
Data Quality
6 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment Vendor VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC No
EPSS 0.0%
Patch available Yes
Active threat No
Deciding rule
CRITICAL severity
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Out-of-Cycle
Exploitation
None
System Exposure· derived
Open
Automatable
Yes
Human Impact
Very High
Technical Impact
Partial

Priority Score

46
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +46
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Related Vulnerabilities in Firefox Multiple Component Vulnerabilities

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CVE-2026-4728 MEDIUM
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CVE-2026-4692 CRITICAL POC
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CVE-2026-4685 HIGH
7.5
CVE-2026-4686 HIGH
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CVE-2026-4687 HIGH
8.6
CVE-2026-4688 CRITICAL
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CVE-2026-4690 HIGH
8.6
CVE-2026-4691 CRITICAL
9.8
CVE-2026-4694 HIGH
7.5
CVE-2026-4705 CRITICAL
9.8
CVE-2026-4724 CRITICAL
9.1

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CVE-2013-0758 CRITICAL POC
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Mozilla Firefox before 18.0, Firefox ESR 10.x before 10.0.12 and 17.x before 17.0.2, Thunderbird before 17.0.2, Thunderb
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9.3 Jan 13

Use-after-free vulnerability in the serializeToStream implementation in the XMLSerializer component in Mozilla Firefox b
CVE-2012-3993 CRITICAL POC
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The Chrome Object Wrapper (COW) implementation in Mozilla Firefox before 16.0, Firefox ESR 10.x before 10.0.8, Thunderbi
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CVE-2013-0757 CRITICAL POC
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CVE-2014-1510 CRITICAL POC
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CVE-2014-1511 CRITICAL POC
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CVE-2013-0643 HIGH
8.8 Feb 27

The Firefox sandbox in Adobe Flash Player before 10.3.183.67 and 11.x before 11.6.602.171 on Windows and Mac OS X, and b

Same weakness CWE-908 – Use of Uninitialized Resource

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CVE-2025-68613 HIGH POC
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CVE-2015-1701 HIGH POC
7.8
CVE-2017-0147 HIGH POC
7.5

Vendor StatusVendor

Debian

firefox
Release Status Fixed Version Urgency
sid vulnerable 148.0.2-1 -
(unstable) fixed (unfixed) -
firefox-esr
Release Status Fixed Version Urgency
bullseye vulnerable 115.14.0esr-1~deb11u1 -
bullseye (security) vulnerable 140.8.0esr-1~deb11u1 -
bookworm vulnerable 128.14.0esr-1~deb12u1 -
bookworm (security) vulnerable 140.8.0esr-1~deb12u1 -
trixie (security), trixie vulnerable 140.8.0esr-1~deb13u1 -
forky, sid vulnerable 140.8.0esr-1 -
(unstable) fixed (unfixed) -

SUSE

Severity: Critical
Product Status
Image SLES15-SP5-SAP-Azure-LI-BYOS Image SLES15-SP5-SAP-Azure-LI-BYOS-Production Image SLES15-SP5-SAP-Azure-VLI-BYOS Image SLES15-SP5-SAP-Azure-VLI-BYOS-Production Image SLES15-SP6-SAP-Azure-LI-BYOS Image SLES15-SP6-SAP-Azure-LI-BYOS-Production Image SLES15-SP6-SAP-Azure-VLI-BYOS Image SLES15-SP6-SAP-Azure-VLI-BYOS-Production Image SLES15-SP7-SAP-Azure-LI-BYOS-Production Image SLES15-SP7-SAP-Azure-VLI-BYOS-Production Affected
SUSE Liberty Linux 10 Fixed
SUSE Liberty Linux 8 Fixed
SUSE Liberty Linux 9 Fixed
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed

References

Advisories & patches
ADVISORY https://access.redhat.com/errata/RHSA-2026:5930 ADVISORY https://access.redhat.com/errata/RHSA-2026:5931 ADVISORY https://access.redhat.com/errata/RHSA-2026:5932 ADVISORY https://access.redhat.com/errata/RHSA-2026:6188 ADVISORY https://access.redhat.com/errata/RHSA-2026:6342 ADVISORY https://access.redhat.com/errata/RHSA-2026:6917 ADVISORY https://access.redhat.com/errata/RHSA-2026:7837 ADVISORY https://access.redhat.com/errata/RHSA-2026:7838 ADVISORY https://access.redhat.com/errata/RHSA-2026:7839 ADVISORY https://access.redhat.com/errata/RHSA-2026:7840 ADVISORY https://access.redhat.com/errata/RHSA-2026:7841 ADVISORY https://access.redhat.com/errata/RHSA-2026:7842 ADVISORY https://access.redhat.com/errata/RHSA-2026:7843 ADVISORY https://access.redhat.com/errata/RHSA-2026:7845 ADVISORY https://access.redhat.com/errata/RHSA-2026:7858 ADVISORY https://access.redhat.com/errata/RHSA-2026:8284 ADVISORY https://access.redhat.com/errata/RHSA-2026:8285 ADVISORY https://access.redhat.com/errata/RHSA-2026:8286 ADVISORY https://access.redhat.com/errata/RHSA-2026:8287 ADVISORY https://access.redhat.com/errata/RHSA-2026:8288 ADVISORY https://access.redhat.com/errata/RHSA-2026:8289 ADVISORY https://access.redhat.com/errata/RHSA-2026:8290 ADVISORY https://access.redhat.com/errata/RHSA-2026:8315 ADVISORY https://access.redhat.com/errata/RHSA-2026:8427 ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-4716 ADVISORY https://vuldb.com/?id.352761 ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1126/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1127/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1163/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:20978/ REF https://bugzilla.mozilla.org/show_bug.cgi?id=2018592 REF https://www.mozilla.org/security/advisories/mfsa2026-20/ REF https://www.mozilla.org/security/advisories/mfsa2026-22/ REF https://www.mozilla.org/security/advisories/mfsa2026-23/ REF https://www.mozilla.org/security/advisories/mfsa2026-24/

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