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Firefox Esr CVE-2026-4698

| EUVDEUVD-2026-14813 CRITICAL
Access of Resource Using Incompatible Type (Type Confusion) (CWE-843)
2026-03-24 mozilla
Information Disclosure Memory Corruption Mozilla Firefox Esr
9.8
CVSS 3.1 · NVD
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Attack ChainAIDerived

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

  1. Access
    Deliver malicious JavaScript to victim
  2. Exploit
    JIT engine miscompiles code
  3. Execution
    Bypass security checks
  4. Impact
    Execute arbitrary code with browser privileges

Vulnerability Assessment

Weakness
CWE
CWE-843
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
ASVS 5.0
V15 - Secure Coding and Architecture Type safety enforcement
MITRE ATT&CK

1 technique across 1 tactic: Execution

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 exploits JIT miscompilation in JavaScript Engine. Victim must visit a malicious webpage or open crafted content in Firefox < 149, Firefox ESR < 115.34, or Firefox ESR < 140.9. No special configuration required; default browser configurations are vulnerable.
Impact

The real-world risk of this vulnerability is moderate to significant, despite the absence of CVSS and EPSS scores in the provided intelligence. The information disclosure impact indicates potential for sensitive data leakage from browser memory. Firefox's ubiquity as a widely-used browser means the affected population is substantial. The vulnerability affects three distinct product lines (mainline Firefox and two ESR branches), suggesting it was discovered during active development and backported to legacy versions. No public exploit (POC) is referenced in the available data, and KEV status is not indicated, suggesting this may not be actively exploited in the wild at disclosure time. However, the technical nature of JIT miscompilation—requiring memory corruption to be leveraged—indicates moderate attack complexity. Organizations should prioritize patching given the information disclosure severity and broad user base, though this is not an emergency-tier remote code execution vulnerability.
Exploit ScenarioDerived

An attacker hosts a malicious website containing specially-crafted JavaScript code designed to trigger JIT miscompilation in the target browser. When a user visits the site, the vulnerable JavaScript engine compiles the malicious code into incorrect native machine instructions that access memory outside intended bounds. The miscompiled code then reads and exfiltrates sensitive data such as authentication tokens, session cookies, or other in-memory secrets to the attacker's server. This attack requires no user interaction beyond visiting a website and no special privileges, making it an attractive vector for mass 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

A JIT miscompilation vulnerability exists in Firefox's JavaScript engine that can lead to information disclosure. This affects Firefox versions below 149, Firefox ESR below 115.34, and Firefox ESR below 140.9. An attacker can exploit this flaw through malicious JavaScript to extract sensitive information from the browser's memory, potentially compromising user data and system security.

RemediationAI

Immediately upgrade Mozilla Firefox to version 149 or later, or upgrade Firefox ESR to version 115.34 or later, or upgrade to version 140.9 or later depending on your deployed ESR branch. These patched versions are available from https://www.mozilla.org/. No partial workarounds exist for JIT miscompilation vulnerabilities; patching is mandatory. Organizations using Firefox in managed environments should deploy automatic updates or enforce version management policies to ensure all users receive the patched versions. Consult the specific security advisories (MFSA2026-20, MFSA2026-21, MFSA2026-22) for detailed patch notes and any platform-specific installation instructions.

Affected VersionsENISA

Firefox ESR unspecified <140.9
Firefox unspecified <149
Firefox ESR unspecified <115.34

Affected Packages

euvd firefox_esr_unspecified fix: 115.34, 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 the JIT (Just-In-Time) compilation component of Firefox's JavaScript engine, which is responsible for dynamically compiling JavaScript bytecode into native machine code for performance optimization. JIT miscompilation occurs when the compiler generates incorrect native code from valid JavaScript source, causing memory safety violations. The affected products per CPE are Mozilla Firefox (cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*) and Mozilla Firefox ESR (cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*). While no specific CWE is listed in the provided data, JIT miscompilation typically falls under CWE-94 (Improper Control of Generation of Code) or CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), allowing attackers to read out-of-bounds memory.

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Severity by source

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 7.5 HIGH

Primary rating from NVD.

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

DescriptionNVD

JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, and Firefox ESR < 140.9.

Zero Day Initiative Advisories

ZDI-26-252 Mozilla Firefox IonMonkey Switch Statement Optimization Type Confusion Remote Code Execution Vulnerability Apr 2026

Executive ViewAI

Why It Matters

CVE-2026-4698 presents critical security risk 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) 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 95% exploitable
Data Quality
7 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

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.

Related Vulnerabilities in Firefox Multiple Memory and Boundary Vulnerabilities

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CVE-2026-4714 HIGH
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CVE-2026-4718 HIGH
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CVE-2026-4719 HIGH
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CVE-2026-4720 CRITICAL
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CVE-2026-4726 HIGH
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CVE-2026-4708 HIGH
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CVE-2026-4722 HIGH
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CVE-2026-4701 CRITICAL
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CVE-2026-4704 HIGH
7.5
CVE-2026-4706 HIGH
7.5
CVE-2026-4707 HIGH
7.5
CVE-2026-4709 HIGH
7.5
CVE-2026-4710 CRITICAL
9.8
CVE-2026-4711 CRITICAL
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CVE-2026-4723 CRITICAL
9.8

More in Firefox Esr

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CVE-2015-4000 LOW POC
3.7 May 21

The TLS protocol 1.2 and earlier, when a DHE_EXPORT ciphersuite is enabled on a server but not on a client, does not pro
CVE-2020-26950 HIGH POC
8.8 Dec 09

In certain circumstances, the MCallGetProperty opcode can be emitted with unmet assumptions resulting in an exploitable

CVE-2026-4689 CRITICAL POC
10.0 Mar 24

A sandbox escape vulnerability exists in Firefox's XPCOM component due to incorrect boundary conditions and integer over
CVE-2022-29917 CRITICAL POC
9.8 Dec 22

Mozilla developers Andrew McCreight, Gabriele Svelto, Tom Ritter and the Mozilla Fuzzing Team reported memory safety bug
CVE-2014-1568 HIGH
7.5 Sep 25

Mozilla Network Security Services (NSS) before 3.16.2.1, 3.16.x before 3.16.5, and 3.17.x before 3.17.1, as used in Mozi
CVE-2022-26384 CRITICAL POC
9.6 Dec 22

If an attacker could control the contents of an iframe sandboxed with <code>allow-popups</code> but not <code>allow-scri
CVE-2022-34484 HIGH POC
8.8 Dec 22

The Mozilla Fuzzing Team reported potential vulnerabilities present in Thunderbird 91.10. Rated high severity (CVSS 8.8)
CVE-2022-28281 HIGH POC
8.8 Dec 22

If a compromised content process sent an unexpected number of WebAuthN Extensions in a Register command to the parent pr
CVE-2022-26381 HIGH POC
8.8 Dec 22

An attacker could have caused a use-after-free by forcing a text reflow in an SVG object leading to a potentially exploi
CVE-2022-22756 HIGH POC
8.8 Dec 22

If a user was convinced to drag and drop an image to their desktop or other folder, the resulting object could have been
CVE-2022-22740 HIGH POC
8.8 Dec 22

Certain network request objects were freed too early when releasing a network request handle. Rated high severity (CVSS

CVE-2022-22738 HIGH POC
8.8 Dec 22

Applying a CSS filter effect could have accessed out of bounds memory. Rated high severity (CVSS 8.8), this vulnerabilit

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

View all
CVE-2011-0611 HIGH POC
8.8
CVE-2012-0507 CRITICAL POC
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CVE-2017-8291 HIGH POC
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CVE-2016-7201 HIGH POC
8.8
CVE-2017-0037 HIGH POC
8.1
CVE-2019-0752 HIGH POC
7.5
CVE-2017-5070 HIGH POC
8.8
CVE-2023-3079 HIGH POC
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Same technique Information Disclosure

View all
CVE-2019-2725 CRITICAL POC
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CVE-2021-34523 CRITICAL POC
9.0
CVE-2013-2251 CRITICAL POC
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CVE-2017-5638 CRITICAL POC
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CVE-2025-24813 CRITICAL POC
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CVE-2025-68613 HIGH POC
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CVE-2015-1701 HIGH POC
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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-2026-4698 ADVISORY https://vuldb.com/?id.352730 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://access.redhat.com/errata/RHSA-2026:8850 REF https://access.redhat.com/security/cve/CVE-2026-4698 REF https://bugzilla.mozilla.org/show_bug.cgi?id=2020906 REF https://bugzilla.redhat.com/show_bug.cgi?id=2450719 REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4698.json REF https://www.mozilla.org/security/advisories/mfsa2026-20/ REF https://www.mozilla.org/security/advisories/mfsa2026-21/ 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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