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Red Hat EUVDEUVD-2026-14837

| CVE-2026-4711 CRITICAL
Use After Free (CWE-416)
2026-03-24 mozilla GHSA-9979-85jw-xp9m
Information Disclosure Use After Free Memory Corruption Red Hat Mozilla Suse
Critical
Disputed · 9.8 NVD
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Attack ChainAIDerived

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

  1. Access
    Send malicious network request
  2. Exploit
    Trigger use-after-free in Widget Cocoa component
  3. Execution
    Corrupt memory state
  4. Impact
    Execute arbitrary code with Firefox privileges

Vulnerability Assessment

Weakness
CWE
CWE-416
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
ASVS 5.0
V15 - Secure Coding and Architecture Memory lifecycle management
MITRE ATT&CK

2 techniques across 2 tactics: Execution, Privilege Escalation

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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Exploitation Conditions

Remote unauthenticated attacker can exploit this vulnerability in Firefox versions below 149 (or Firefox ESR below 140.9) through network without user interaction. The Widget: Cocoa component processes untrusted data, triggering the use-after-free condition on default installations.
Impact

Although CVSS score and vector are not available from the advisory, the vulnerability is tagged as enabling information disclosure, suggesting at minimum a confidentiality impact. The vulnerability was disclosed by Mozilla in two security advisories (MFSA2026-20 and MFSA2026-22), indicating coordinated disclosure with defined patch releases. The use-after-free class (CWE-416) in browser UI components typically carries moderate to high severity due to potential for memory corruption leading to arbitrary code execution on macOS. Without CVSS, EPSS, or KEV status data, the real-world exploitability cannot be quantified precisely, but use-after-free bugs in browser components are generally considered practically exploitable when memory layout is predictable. The fact that specific version cutoffs (Firefox 149, Firefox ESR 140.9) were released suggests patches are available, reducing active exploitation likelihood for patched systems. Priority should be HIGH for unpatched macOS Firefox users, particularly those in high-risk threat environments.
Exploit ScenarioDerived

An attacker could craft a malicious website or WebExtension that triggers the use-after-free condition in the Cocoa widget framework through specific UI interaction sequences or rendering operations. When a macOS user visits this site or loads the malicious extension, the vulnerability allows the attacker to read sensitive memory contents (browser credentials, cached data) or, with additional heap grooming techniques, potentially execute arbitrary code with Firefox process privileges. The attack requires user interaction (visiting the site/installing extension) and targets only macOS users, limiting the attack surface compared to cross-platform vulnerabilities.
Act Now Prioritize within 24-48h. Why: CRITICAL severity.
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 24, 2026

A use-after-free vulnerability in Firefox's Cocoa widget component allows remote code execution without user interaction or special privileges, affecting Firefox versions below 149 and ESR below 140.9. An attacker can exploit this memory corruption flaw over the network to achieve complete system compromise with high confidentiality, integrity, and availability impact. No patch is currently available.

Earlier versions of this analysis (1)
v1 Mar 24, 2026 - 12:45 CVSS 9.8

A use-after-free vulnerability exists in the Widget: Cocoa component of Mozilla Firefox and Firefox ESR, allowing potential information disclosure or code execution depending on exploitation context. Firefox versions below 149 and Firefox ESR versions below 140.9 are affected. An attacker could potentially trigger this memory safety vulnerability through malicious web content or other attack vectors to read sensitive information or execute arbitrary code on affected systems.

RemediationAI

Upgrade Mozilla Firefox to version 149 or later, and Firefox ESR to version 140.9 or later, on all affected macOS systems. Users should check https://www.mozilla.org/security/advisories/mfsa2026-20/ and https://www.mozilla.org/security/advisories/mfsa2026-22/ for specific release notes and download locations. For enterprise deployments, enable automatic updates or use centralized patch management to distribute these critical updates promptly. Until patching is possible, users should minimize exposure by limiting browser use on untrusted networks and disabling JavaScript from potentially malicious sources where operationally feasible, though these are incomplete mitigations for a Cocoa framework vulnerability.

Affected VersionsENISA

Firefox unspecified <149
Firefox ESR unspecified <140.9

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

This vulnerability resides in the Widget: Cocoa component, which is Mozilla's native macOS user interface framework responsible for rendering browser chrome and handling native UI interactions. The use-after-free (CWE-416) is a memory safety vulnerability where code attempts to access memory that has been freed, potentially allowing attackers to read adjacent memory contents or corrupt memory state. The Cocoa framework, being platform-specific to macOS, means this vulnerability exclusively affects macOS users running Firefox or Firefox ESR. The affected products are identified via CPE strings cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* and cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*, indicating all versions of Firefox and Firefox ESR before the patched releases.

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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 9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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
High
Availability
High

Lifecycle Timeline

2
Patch released
Mar 31, 2026 - 21:13 nvd
Patch available
CVE Published
Mar 24, 2026 - 12:30 nvd
CRITICAL 9.8

DescriptionCVE.org

Use-after-free in the Widget: Cocoa component. This vulnerability affects Firefox < 149 and Firefox ESR < 140.9.

Executive ViewAI

Why It Matters

CVE-2026-4711 presents critical security risk, a use-after-free vulnerability rated CVSS 9.8. 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) Enable ASLR and DEP where available; (2) Implement network segmentation; (3) Monitor for exploitation indicators.

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
Total

Priority Score

49
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +49
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Use After Free HIGH

Use-after-free vulnerabilities occur when a program continues to access memory through a pointer after that memory has been deallocated.

Memory Corruption HIGH

Memory corruption occurs when a program writes data beyond the boundaries of allocated memory regions or accesses memory in unintended ways, violating the integrity of the process's address space.

Information Disclosure MEDIUM

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

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Use-after-free vulnerability in the serializeToStream implementation in the XMLSerializer component in Mozilla Firefox b
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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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Same weakness CWE-416 – Use After Free

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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-2026-4711 ADVISORY https://vuldb.com/?id.352757 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=2017002 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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