Firefox Esr CVE-2026-4688

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EUVD

EUVD-2026-14800 CRITICAL

Use After Free (CWE-416)

2026-03-24 mozilla

GHSA-7364-g429-cg4v

Information Disclosure Use After Free Memory Corruption 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

Access

Send malicious webpage to Firefox browser
Exploit

Trigger use-after-free in Disability Access APIs
Execution

Escape sandbox isolation
Impact

Execute arbitrary code with system 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Weakness	CWE CWE-416 OWASP Top 10:2025 A06:2021 - Vulnerable and Outdated Components ASVS 5.0 V15 - Secure Coding and Architecture Memory lifecycle management MITRE ATT&CK 2 techniques across 2 tactics: Execution, Privilege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. Sign in to read
Exploitation Conditions	Remote unauthenticated attacker can exploit Firefox versions before 149 (or Firefox ESR before 140.9) without user interaction. No special configuration required. Attacker sends malicious network content triggering use-after-free in Disability Access APIs, escaping sandbox and compromising system.
Impact	This vulnerability represents a critical security risk due to its sandbox-escape nature, which is consistently one of the highest-impact threat classes in browser security. Although CVSS and CVSS vector data are unavailable in the provided intelligence, the sandbox escape capability indicates this would likely score in the critical range (9.0+) with a network-based attack vector and low complexity. The Mozilla security advisories (MFSA2026-20 and MFSA2026-22) indicate this was formally disclosed through vendor channels, suggesting coordinated disclosure practices were followed. The lack of public POC or KEV listing at the time of this analysis suggests active in-the-wild exploitation may be limited, but the technical impact is severe: an attacker chain combining this vulnerability with standard web exploitation could bypass Firefox's multi-process architecture and sandbox restrictions entirely. Real-world priority should be extremely high for any organization running affected Firefox versions, particularly in environments where users visit untrusted websites.
Exploit ScenarioDerived	An attacker hosts a malicious website containing specially crafted JavaScript that triggers a use-after-free condition in the Disability Access APIs component. When a victim visits the site with a vulnerable Firefox version, the attacker's code causes freed memory to be reallocated under attacker control, enabling arbitrary code execution within the Firefox process. From this point, the attacker can break the sandbox boundary and gain privileged access to the underlying operating system, steal credentials, install malware, or pivot to other systems on the network.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.

Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 24, 2026

Sandbox escape in Mozilla Firefox's Disability Access APIs component due to a use-after-free memory vulnerability allows unauthenticated remote attackers to execute arbitrary code with full system compromise. Firefox versions below 149 and Firefox ESR below 140.9 are affected, with no patch currently available. The vulnerability is exploitable over the network without user interaction, presenting critical risk to all affected users.

Earlier versions of this analysis (1)

v1 Mar 24, 2026 - 12:45 CVSS 10.0

A use-after-free vulnerability exists in Firefox and Firefox ESR's Disability Access APIs component that allows attackers to escape the browser sandbox and potentially achieve arbitrary code execution. The vulnerability affects Firefox versions below 149 and Firefox ESR versions below 140.9. An attacker can exploit this memory safety flaw to break out of the sandbox environment, gaining access to system resources beyond the browser's intended security boundary.

RemediationAI

Immediately upgrade Firefox to version 149 or later and Firefox ESR to version 140.9 or later to patch the use-after-free vulnerability. Users unable to update immediately should restrict their browsing to trusted, HTTPS-enabled sites and consider disabling accessibility features if not required, though this is not a complete mitigation. Organizations should prioritize patching Firefox across all endpoints, as sandbox escape vulnerabilities can lead to system compromise and should be treated with the same urgency as operating system kernel vulnerabilities. Consult the official Mozilla security advisories at https://www.mozilla.org/security/advisories/mfsa2026-20/ and https://www.mozilla.org/security/advisories/mfsa2026-22/ for detailed patch delivery mechanisms and any additional guidance.

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

The vulnerability is rooted in a use-after-free memory safety issue within the Accessibility (a11y) APIs component, which is responsible for exposing browser internals to assistive technologies. Use-after-free flaws occur when code attempts to access memory that has already been freed, potentially allowing an attacker to control freed memory regions and execute arbitrary code. The affected products are identified via CPE as Mozilla Firefox (cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*) and Firefox ESR (cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*), indicating all versions prior to the patched releases are vulnerable. The Disability Access APIs, while designed to improve accessibility, expose a larger attack surface by bridging the gap between web content and system-level accessibility services, making memory safety critical in this component.

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Exploit and PoC references, threat intelligence from 22 sources

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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 due to use-after-free in the Disability Access APIs component. This vulnerability affects Firefox < 149 and Firefox ESR < 140.9.

Executive ViewAI

Why It Matters

Organizations using the Disability Access APIs component. This vulnerability affects Firefox face critical risk from CVE-2026-4688, a use-after-free vulnerability 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) Enable ASLR and DEP where available; (2) Implement network segmentation; (3) Monitor for exploitation indicators.

Threat Intelligence Overview

EPSS Score

0.0%

Top 95% exploitable

Data Quality

7 sources

Confidence: High

EUVD

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

Scheduled

Exploitation

None

System Exposure· derived

Open

Automatable

No

Human Impact

Very High

Technical Impact

Total

Priority Score

50

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +50

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.

Related Vulnerabilities in Firefox Multiple Component Vulnerabilities

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CVE-2026-4725 CRITICAL

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CVE-2026-4728 MEDIUM

CVE-2026-4692 CRITICAL POC

CVE-2026-4685 HIGH

CVE-2026-4686 HIGH

CVE-2026-4687 HIGH

CVE-2026-4690 HIGH

CVE-2026-4691 CRITICAL

CVE-2026-4694 HIGH

CVE-2026-4705 CRITICAL

CVE-2026-4724 CRITICAL

More in Firefox Esr

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CVE-2015-4000 LOW Monitor POC

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 Act Now POC

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

CVE-2026-4689 CRITICAL Act Now POC

A sandbox escape vulnerability exists in Firefox's XPCOM component due to incorrect boundary conditions and integer over

CVE-2022-29917 CRITICAL Act Now POC

Mozilla developers Andrew McCreight, Gabriele Svelto, Tom Ritter and the Mozilla Fuzzing Team reported memory safety bug

CVE-2014-1568 HIGH Act Now

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 Act Now POC

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 This Week POC

The Mozilla Fuzzing Team reported potential vulnerabilities present in Thunderbird 91.10. Rated high severity (CVSS 8.8)

CVE-2022-28281 HIGH This Week POC

If a compromised content process sent an unexpected number of WebAuthN Extensions in a Register command to the parent pr

CVE-2022-26381 HIGH This Week POC

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 This Week POC

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 This Week POC

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

CVE-2022-22738 HIGH This Week POC

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

Same weakness CWE-416 – Use After Free

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CVE-2019-0708 CRITICAL POC

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CVE-2014-0322 HIGH POC

CVE-2012-4792 HIGH POC

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CVE-2015-0313 CRITICAL POC

CVE-2015-5122 CRITICAL POC

CVE-2013-2551 HIGH POC

Same technique Information Disclosure

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CVE-2019-2725 CRITICAL POC

CVE-2021-34523 CRITICAL POC

CVE-2013-2251 CRITICAL POC

CVE-2017-5638 CRITICAL POC

CVE-2025-24813 CRITICAL POC

CVE-2025-68613 HIGH POC

CVE-2015-1701 HIGH POC

CVE-2017-0147 HIGH POC

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-2026-4688 ADVISORY https://vuldb.com/?id.352735 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-2026-4688 REF https://bugzilla.mozilla.org/show_bug.cgi?id=2016373 REF https://bugzilla.redhat.com/show_bug.cgi?id=2450713 REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4688.json 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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