Firefox Esr CVE-2026-4693

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EUVD

EUVD-2026-14808 HIGH

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

2026-03-24 mozilla

GHSA-6956-6r33-f8xw

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

Craft malformed audio/video file
Delivery

Host file on attacker-controlled server
Exploit

Trigger playback in vulnerable Firefox
Execution

Boundary condition violation in parser
Impact

Denial of service via crash

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 audio/video content to Firefox < 149, Firefox ESR < 115.34, or Firefox ESR < 140.9. Victim must open or play the malicious media file in Firefox. No special browser configuration required.
Impact	The risk profile for CVE-2026-4693 presents mixed signals due to incomplete disclosure data. CVSS and CVSS vector information are not available, limiting quantitative severity assessment. However, the vulnerability is tagged as 'Information Disclosure' rather than Remote Code Execution, suggesting a more limited immediate impact than memory safety issues that enable arbitrary code execution. The vulnerability affects three widely-deployed Firefox release channels across millions of users globally, indicating broad exposure. No KEV (Known Exploited Vulnerability) status, POC availability, or EPSS score is documented in the intelligence sources, suggesting this may be a pre-release disclosure or a patched vulnerability without active real-world exploitation documented at time of analysis. The Mozilla security advisories (MFSA2026-20, MFSA2026-21, MFSA2026-22) indicate coordinated disclosure across multiple Firefox versions. Given the information disclosure classification and lack of confirmed active exploitation, this appears to be a moderately prioritized vulnerability requiring timely patching but not an emergency-level threat requiring immediate mitigation outside normal update cycles.
Exploit ScenarioDerived	An attacker crafts a malicious audio or video file with specially crafted boundary markers that trigger the boundary condition flaw during playback. When a victim visits a compromised website or opens a malicious media file in Firefox, the audio/video decoding process reads beyond the intended memory buffer, leaking sensitive information such as authentication tokens, cached credentials, or fragments of previously processed data. The information is then exfiltrated through JavaScript or covert channels embedded in the malicious media container, allowing the attacker to hijack user sessions or access sensitive data without requiring explicit user code execution.

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

An incorrect boundary condition vulnerability exists in the Audio/Video playback component of Mozilla Firefox, affecting Firefox versions below 149, Firefox ESR below 115.34, and Firefox ESR below 140.9. This flaw enables information disclosure through improper memory boundary handling during media playback operations. While specific exploit details and CVSS metrics are not publicly disclosed, the vulnerability is categorized as an information disclosure issue affecting all three Firefox release channels.

RemediationAI

Immediately upgrade Mozilla Firefox to version 149 or later via the browser's built-in update mechanism (Help > About Firefox on most platforms). For Firefox ESR deployments, upgrade to either version 115.34 or version 140.9 or later depending on which ESR branch your organization maintains. Consult https://www.mozilla.org/security/advisories/mfsa2026-20/, mfsa2026-21/, and mfsa2026-22/ for detailed patch notes and compatibility information. For environments unable to patch immediately, restrict user access to untrusted media sources and disable auto-play of media content via browser policies (enterprise.json configuration on Windows or distribution/policies.json on Linux/macOS). Implement network-level monitoring for suspicious media file access patterns as a temporary compensating control.

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 resides in Firefox's Audio/Video playback subsystem, which handles decoding and rendering of multimedia content. Incorrect boundary condition checks in this component allow attackers to read beyond allocated memory regions during media processing. The affected products are Mozilla Firefox (all versions, as per CPE cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*) and Firefox ESR across two maintenance branches (cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*). While a specific CWE identifier was not provided in the intelligence data, boundary condition errors typically map to CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) or CWE-125 (Out-of-bounds Read), both critical memory safety classes. The root cause involves inadequate validation of buffer boundaries during audio/video frame parsing or rendering operations.

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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 Audio/Video: Playback component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, and Firefox ESR < 140.9.

Executive ViewAI

Why It Matters

CVE-2026-4693 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.

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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-2026-4693 ADVISORY https://vuldb.com/vuln/352744 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-2026-4693 REF https://bugzilla.mozilla.org/show_bug.cgi?id=2018102 REF https://bugzilla.redhat.com/show_bug.cgi?id=2450741 REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4693.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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