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Firefox Esr CVE-2026-4692

| EUVDEUVD-2026-14807 CRITICAL
Improper Isolation or Compartmentalization (CWE-653)
2026-03-24 mozilla GHSA-cm3f-xp4p-xgj7
Information Disclosure Mozilla Firefox Esr
10.0
CVSS 3.1 · NVD
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Attack ChainAIDerived

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

  1. Access
    Open Firefox browser
  2. Delivery
    Access Responsive Design Mode feature
  3. Exploit
    Trigger sandbox escape vulnerability
  4. Execution
    Execute arbitrary code outside sandbox
  5. Impact
    Achieve system-level compromise

Vulnerability Assessment

Weakness
CWE
CWE-653
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V15 - Secure Coding and Architecture Component isolation
Exploitation Conditions

The victim must have Firefox < 149, Firefox ESR < 115.34, or Firefox ESR < 140.9 open with Responsive Design Mode enabled. Remote attacker can deliver malicious content via network (e.g., website) without authentication. No victim interaction needed beyond visiting the page.
Impact

While CVSS score and vector data are not provided for this vulnerability, sandbox escape defects are inherently high-severity due to their technical impact: they enable privilege escalation from untrusted content to browser process capabilities. The vulnerability is tagged as Information Disclosure, suggesting the primary impact is confidentiality breach rather than code execution or system compromise, which may moderate overall severity compared to remote code execution flaws. The presence of multiple Firefox Security Advisories (MFSA2026-20, MFSA2026-21, MFSA2026-22) indicates Mozilla has released coordinated patches. Without EPSS data, KEV confirmation, or public POC information visible in the references, the real-world exploitation probability appears to be in the early disclosure phase. However, the specificity of the vulnerability (named component, clear version boundaries) and the involvement of developer tools (which may be used by targeted high-value users) suggest this should be prioritized for rapid patching despite the absence of active exploitation signals. The presence of three separate security advisories suggests this may be part of a broader Firefox security release.
Exploit ScenarioDerived

An attacker could craft a malicious webpage that, when opened in Firefox, exploits the Responsive Design Mode sandbox escape to access the browser's privilege context and exfiltrate sensitive user information such as browsing history, stored credentials, or data from other open tabs. If a developer or security researcher opens the attacker's page while using Firefox's developer tools (which is plausible given the vulnerability's location in the Responsive Design Mode component), the attack would succeed without additional user interaction beyond opening the page. The information disclosure capability suggests the attacker gains read access to sensitive data rather than achieving arbitrary code execution, though the sandbox escape itself could potentially be chained with other vulnerabilities for greater impact.
Act Now Prioritize within 24-48h. Why: CRITICAL severity + public POC available.
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 24, 2026

A sandbox escape vulnerability exists in Firefox's Responsive Design Mode component that allows attackers to break out of the browser's security sandbox and access sensitive information. This affects Firefox versions prior to 149, Firefox ESR prior to 115.34, and Firefox ESR prior to 140.9. An attacker can exploit this vulnerability to disclose information by circumventing the sandbox restrictions that normally isolate web content from the browser's privileged context.

RemediationAI

Immediately upgrade Firefox to version 149 or later, or upgrade Firefox ESR to version 115.34 or later (or 140.9 or later depending on your ESR branch). Users can verify their current version via Help > About Firefox, which will automatically download available updates. For enterprise deployments using Firefox ESR, coordinate with your ESR branch maintainer to ensure timely distribution of the patched versions. Until patching is completed, users should avoid using the Responsive Design Mode feature if possible, and should restrict Firefox usage to trusted websites. System administrators can enforce automatic Firefox updates via group policy or mobile device management tools. Monitor the referenced Mozilla security advisories for any additional guidance or related vulnerabilities that may be disclosed alongside this fix.

Affected VersionsENISA

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

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 Responsive Design Mode is a Firefox developer tools feature that allows testing website layouts at different screen sizes and device configurations. This component operates within a sandboxed environment to prevent malicious web pages from accessing browser internals and system resources. The vulnerability represents a sandbox escape, a critical class of defect where the isolation boundary between untrusted content and privileged browser code is compromised. While the specific CWE classification is not provided in the vulnerability data, sandbox escapes typically fall under CWE-693 (Protection Mechanism Failure) or related memory safety and privilege escalation categories. The affected products are identified via CPE strings as Mozilla Firefox (cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*) and Mozilla Firefox ESR (cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*), indicating all versions within the vulnerable ranges are affected regardless of platform or configuration.

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Severity by source

NVD PRIMARY 10.0 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
SUSE 9.6 CRITICAL
AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Red Hat 7.5 HIGH

Primary rating from NVD.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Changed
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 10.0

DescriptionNVD

Sandbox escape in the Responsive Design Mode component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, and Firefox ESR < 140.9.

Executive ViewAI

Why It Matters

Organizations using the Responsive Design Mode component. This vulnerability affects Firefox face critical risk from CVE-2026-4692 rated CVSS 10.0. 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 99% exploitable
Exploit
POC
Public exploit code exists
Data Quality
7 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment Vendor GitHub 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 Yes
EPSS 0.0%
Patch available Yes
Active threat No
Deciding rule
CRITICAL severity + public POC available
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
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact
Very High
Technical Impact
Total

Priority Score

70
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +50
PoC: +20
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-2026-4684 HIGH
7.5
CVE-2026-4716 CRITICAL
9.1
CVE-2026-4725 CRITICAL
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CVE-2026-4727 HIGH
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CVE-2026-4728 MEDIUM
6.5
CVE-2026-4685 HIGH
7.5
CVE-2026-4686 HIGH
7.5
CVE-2026-4687 HIGH
8.6
CVE-2026-4688 CRITICAL
10.0
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

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-653 – Improper Isolation or Compartmentalization

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CVE-2025-1974 CRITICAL POC
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8.2
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CVE-2026-34775 CRITICAL
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CVE-2024-35425 MEDIUM POC
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Same technique Information Disclosure

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CVE-2019-2725 CRITICAL POC
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CVE-2013-2251 CRITICAL POC
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CVE-2017-5638 CRITICAL POC
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CVE-2025-24813 CRITICAL POC
9.8
CVE-2025-68613 HIGH POC
8.8
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-2026-4692 ADVISORY https://vuldb.com/vuln/352740 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-2026-4692 REF https://bugzilla.mozilla.org/show_bug.cgi?id=2017643 REF https://bugzilla.redhat.com/show_bug.cgi?id=2450748 REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4692.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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