Firefox Esr CVE-2026-4685

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EUVD

EUVD-2026-14794 HIGH

Improper Check for Unusual or Exceptional Conditions (CWE-754)

2026-03-24 mozilla

Information Disclosure Mozilla Firefox Esr

7.5

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 Canvas2D drawing commands
Exploit

Trigger boundary condition violation in graphics renderer
Execution

Cause memory access violation
Impact

Crash Firefox process

Vulnerability Assessment

Weakness	CWE CWE-754 OWASP Top 10:2025 A10:2025 - Mishandling of Exceptional Conditions ASVS 5.0 V16 - Security Logging and Error Handling Unusual condition handling
Exploitation Conditions	Remote unauthenticated attacker sends crafted network traffic triggering Canvas2D boundary condition in Firefox < 149, Firefox ESR < 115.34, or Firefox ESR < 140.9. No user interaction required. Affects default browser installations.
Impact	Without CVSS scoring or EPSS probability data in the intelligence provided, the risk assessment relies on structural indicators. The vulnerability is classified as Information Disclosure, which typically has moderate to significant real-world impact since it enables unauthorized data access rather than system compromise or code execution. The presence of multiple Firefox advisory references (MFSA2026-20, MFSA2026-21, MFSA2026-22) suggests this is a formally acknowledged, tracked vulnerability with official patches available. The fact that three separate ESR and main-branch advisory notices were issued indicates Mozilla views this as a priority fix. However, without active exploitation reports or public proof-of-concept code cited, this appears to be a proactively disclosed and patched vulnerability rather than an in-the-wild exploited threat. Organizations should prioritize patching based on their Firefox deployment scale, but this is not an emergency zero-day scenario. The boundary condition flaw in a widely-used rendering engine does carry moderate priority given Firefox's use in both consumer and enterprise environments.
Exploit ScenarioDerived	An attacker could craft a malicious web page containing Canvas2D drawing commands that exploit the boundary condition flaw. When a user visits this page in a vulnerable Firefox version, the attacker's Canvas2D operations would access memory regions outside the intended bounds, potentially reading sensitive data such as authentication tokens, cached credentials, or data from other browser tabs or extensions. The attack vector would be network-based with low to moderate complexity (requiring careful crafting of Canvas2D commands), and no special user privileges would be required—simply visiting the malicious page would trigger the vulnerability.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 24, 2026

This vulnerability involves incorrect boundary conditions in Firefox's Graphics Canvas2D component that enables information disclosure. Firefox versions prior to 149, Firefox ESR prior to 115.34, and Firefox ESR prior to 140.9 are affected. An attacker can leverage improper boundary validation in Canvas2D operations to read sensitive information from memory that should not be accessible through normal web content restrictions.

RemediationAI

Upgrade Firefox to version 149 or later, Firefox ESR to version 115.34 or later, or Firefox ESR to version 140.9 or later, depending on your deployment branch. These patched versions include fixes for the Canvas2D boundary condition flaw and are available directly from Mozilla at https://www.mozilla.org/security/advisories/mfsa2026-20/, https://www.mozilla.org/security/advisories/mfsa2026-21/, and https://www.mozilla.org/security/advisories/mfsa2026-22/. Organizations unable to immediately patch should consider restricting Canvas2D usage on untrusted content or implementing content security policies (CSP) to limit exposure to potentially malicious Canvas2D operations. For enterprise deployments, staged rollout of the patched versions is recommended to validate compatibility before organization-wide deployment.

Affected VersionsENISA

Firefox unspecified <149

Firefox ESR unspecified <140.9

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 exists in the Graphics Canvas2D component, which is responsible for rendering 2D graphics operations within Firefox browsers. Canvas2D is a core component that processes drawing commands and pixel operations. The root cause is classified as an incorrect boundary condition issue, meaning that validation checks designed to prevent out-of-bounds memory access in Canvas2D operations are flawed or incomplete. This allows memory regions outside intended boundaries to be accessed or read. The affected products are identified via CPE: cpe:2.3:a:mozilla:firefox (all versions) and cpe:2.3:a:mozilla:firefox_esr (all versions), indicating the vulnerability is present across the main Firefox release branch and all Extended Support Release (ESR) versions until the specified patched versions.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 7.5 HIGH

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

SUSE HIGH

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

None

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

HIGH 7.5

DescriptionNVD

Incorrect boundary conditions in the Graphics: Canvas2D component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, and Firefox ESR < 140.9.

Executive ViewAI

Why It Matters

CVE-2026-4685 presents notable security risk rated CVSS 7.5. Exploitation could compromise the security of affected deployments. Organizations should apply vendor updates when available and consider compensating controls in the interim.

Business Impact: High

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

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 HIGH

CISA KEV No

Public POC No

EPSS 0.0%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

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

Yes

Human Impact

High

Technical Impact

Partial

Priority Score

38

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +38

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-2026-4725 CRITICAL

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CVE-2026-4728 MEDIUM

CVE-2026-4692 CRITICAL POC

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CVE-2026-4687 HIGH

CVE-2026-4688 CRITICAL

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CVE-2026-4691 CRITICAL

CVE-2026-4694 HIGH

CVE-2026-4705 CRITICAL

CVE-2026-4724 CRITICAL

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

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CVE-2022-34484 HIGH This Week POC

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An attacker could have caused a use-after-free by forcing a text reflow in an SVG object leading to a potentially exploi

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Same weakness CWE-754 – Improper Check for Unusual or Exceptional Conditions

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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: High

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-2026-4685 ADVISORY https://vuldb.com/?id.352737 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-2026-4685 REF https://bugzilla.mozilla.org/show_bug.cgi?id=2016349 REF https://bugzilla.redhat.com/show_bug.cgi?id=2450724 REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4685.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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