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Firefox Esr CVE-2026-4695

| EUVDEUVD-2026-14810 HIGH
Improper Check for Unusual or Exceptional Conditions (CWE-754)
2026-03-24 mozilla GHSA-vxpv-c2h6-hq9v
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

  1. Access
    Attacker sends malformed audio/video stream
  2. Exploit
    Web Codecs parser fails boundary check
  3. Execution
    Memory corruption triggered
  4. Impact
    Denial of service condition achieved

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 can trigger denial of service by sending crafted audio/video content to Firefox < 149 or Firefox ESR < 140.9. No user interaction required; vulnerability in Web Codecs component processing. Default installations affected.
Impact

While CVSS and EPSS scores are not provided, the vulnerability is categorized as information disclosure with no indication of code execution capability, suggesting moderate severity. The affected versions are clearly defined (Firefox < 149 and ESR < 140.9), indicating Mozilla has already released patches. The tag classification as 'Information Disclosure' rather than critical impact limits the real-world risk compared to remote code execution vulnerabilities. However, information disclosure from web codecs could expose cryptographic material, session tokens, or other sensitive data processed during media streaming. Given that this affects two widely-deployed Firefox branches and Mozilla has published security advisories (MFSA2026-20 and MFSA2026-22), this should be treated as a moderate-priority patch requiring timely deployment, particularly for users processing sensitive media content. The lack of CVSS vector data prevents detailed SSVC scoring, but the boundary condition nature suggests this requires user interaction (video/audio processing) to trigger.
Exploit ScenarioDerived

An attacker hosts a malicious website containing crafted WebCodecs operations that trigger incorrect boundary condition handling in Firefox's audio or video codec processing. When a victim visits the site and interacts with embedded media (such as attempting to play a specially-crafted audio or video stream), the boundary condition is triggered, allowing the attacker's JavaScript to read adjacent memory regions. This could expose sensitive data such as cryptographic keys, authentication tokens, or personal information previously processed by the browser. The attack requires the victim to visit the malicious site and engage with media content, but no user-installed plugins or additional vulnerabilities are needed for exploitation.
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

A boundary condition vulnerability exists in Firefox's Audio/Video Web Codecs component that allows information disclosure to attackers. Firefox versions prior to 149 and Firefox ESR versions prior to 140.9 are affected. An attacker can exploit incorrect boundary condition handling in codec processing to read sensitive memory contents or application state.

RemediationAI

Immediately upgrade Firefox to version 149 or later, and Firefox ESR to version 140.9 or later. Both updates contain patches for the boundary condition vulnerability in the Web Codecs component. Users should enable automatic updates in Firefox preferences to ensure timely patching of future vulnerabilities. For enterprise environments unable to immediately patch, restrict user access to untrusted websites that use advanced audio/video streaming features (WebCodecs APIs) until upgrades are completed. Organizations managing Firefox ESR deployments should prioritize this update in their patch management cycle, as ESR releases often have longer deployment windows but still receive security patches on the same schedule as rapid-release Firefox.

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 resides in the Audio/Video Web Codecs component, a critical subsystem responsible for encoding and decoding multimedia streams in web browsers. Web Codecs handle raw audio and video frame data processing at the native code level, making boundary condition errors particularly dangerous as they can lead to out-of-bounds memory access. The affected products are Mozilla Firefox (cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*) and Mozilla Firefox ESR (cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*). The root cause appears to be improper validation of buffer boundaries during codec operations, which is a classic memory safety issue (CWE category for buffer over-read scenarios). This occurs in low-level codec implementations where strict boundary enforcement is essential to prevent memory disclosure.

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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: Web Codecs component. This vulnerability affects Firefox < 149 and Firefox ESR < 140.9.

Executive ViewAI

Why It Matters

CVE-2026-4695 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 97% 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 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 Memory and Boundary Vulnerabilities

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9.8
CVE-2026-4711 CRITICAL
9.8
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9.8

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

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7.5 Sep 25

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CVE-2022-34484 HIGH POC
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The Mozilla Fuzzing Team reported potential vulnerabilities present in Thunderbird 91.10. Rated high severity (CVSS 8.8)
CVE-2022-28281 HIGH POC
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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
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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
CVE-2022-22756 HIGH POC
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If a user was convinced to drag and drop an image to their desktop or other folder, the resulting object could have been
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Applying a CSS filter effect could have accessed out of bounds memory. Rated high severity (CVSS 8.8), this vulnerabilit

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-2026-4695 ADVISORY https://vuldb.com/?id.352742 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-2026-4695 REF https://bugzilla.mozilla.org/show_bug.cgi?id=2020030 REF https://bugzilla.redhat.com/show_bug.cgi?id=2450715 REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4695.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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